THURSDAY, NOVEMBER 28, 1878 RAMSAY'S MANUAL OF BRITISH GEOLOGY THIS HIS well-known work has now reached its fifth edition, and has undergone such changes that it may be almost regarded as a new book. Not only has the quantity of matter in it been almost doubled since the last edition, and its bulk and price augmented in the same proportion, but its plan has been very greatly modified, as is indeed indicated by the second title now prefixed to it. The original work was justly deserving of the very great success which it achieved. It consisted of a corrected report of one of the well-known series of lectures to working-men delivered by the author in his capacity of Professor of Geology in the Royal School of Mines, at the Museum in Jermyn Street; and it was a model of clear exposition of a branch of science by one who was a master of his subject, and who at the same time had acquired great experience and skill in presenting it to popular audiences. Probably no better introduction to the principles of geology could possibly be recommended to the English reader than this little book of Prof. Ramsay's. We must confess to feeling that this complete remodelling of the plan of a work that has already proved so successful, is a somewhat hazardous experiment. The original chapters of the book, which still retain the characteristics of popular lectures, do not always harmonise in style with the portions that were primarily intended for the pages of an encyclopædia. Indeed, as is admitted in the preface, the book now consists of two distinct works fused into one, and the reader is again and again reminded of the fact by somewhat awkward transitions and by abrupt changes in style and in the mode of treatment of the subject. very prominent part. We are bound to say that in respect to these matters he writes with the most perfect candour, and is ever ready to admit that there are subjects in which the timidity or caution of other geologists does not permit them to follow him in his bold generalisations. The space at our disposal will not permit of our entering into detail on the numerous interesting questions suggested by a perusal of this book. The author's attempts to picture to the mind of his readers the ancient physical geography of our portion of the globe. during successive geological periods may be cited as among the most graphic pieces of writing, and at the same time the most valuable portions of the work. Here Prof. Ramsay is evidently entirely in his element; he writes with an enthusiasm which is perfectly contagious, and his arguments, if not always sufficient to carry conviction, are at all times worthy of serious consideration. We cannot resist quoting Prof. Ramsay's latest views on the important and much-vexed question of the classification of the Cambrian and Silurian rocks. On this subject he remarks : "If these strata were to be classified for the first time in England, with my present knowledge, I would divide them into three, as the most convenient method. The first series would include the purple and green grits and slates of the Longwynd and Wales, and range upwards as high as the top of the Tremadoc slates; the second would range from the base of the Arenig slates to the top of the Bala or Caradoc beds; and the third from the base of the Upper Llandovery beds to the top of the Ludlow rocks.' It is true that after this statement, which is in such perfect harmony with the results arrived at by palæontologists in Bohemia, Scandinavia, America, and our own country, Prof. Ramsay announces his intention of still adopting the nomenclature of Murchison and the Geological Survey, which he admits to be "old-fashioned; but he states that his reason for doing so is simply that this plan will be the most convenient for those who wish to consult the geological maps and sections published by the Government. As the date fixed for the completion of the Government Survey is now passed, we may perhaps hope that the Director-General will be able to devote his attention to the much-needed reform of that old-fashioned classification and nomenclature. At all events, every geologist will be gratified by learning from so high an authority that any difference which may now exist concerning the classification of the older palæozoic rocks is mainly one as to the employment of certain terms, and that on the actual facts of the case something like substantial agreement has at last been arrived at. In almost every other respect we find the work to be VOL. XIX,-No. 474 On another question, that of the date of the earliest traces of human workmanship in this country, Prof. Ramsay's remarks are certainly not calculated to give quite so much satisfaction to his readers, He writes :"The antiquity of man being thus clearly established, it becomes obvious that his advent into our area was either E portion of the brick-earth in which the implements were found at Botany Bay, near Thetford, in Suffolk. The announcement at once provoked strenuous opposition, and therefore, on a tour of inspection of Mr. Skertchly's work with Mr. Bristow, we took care to examine into this point. The result was that I satisfied myself of the truth of Mr. Skertchly's observations that the implement bearing brick-earth in places underlies a boulder-clay, which, in his opinion, is not of the earliest date, in which case the men who made these tools must have been of inter-glacial age." The 66 strenuous opposition" to which Prof. Ramsay refers, was directed, it will be remembered, not against the possibility of human remains being found under glacial deposits, but against such a conclusion being accepted without the clearest and most irrefragable evidence being | adduced in its support. And it must be borne in mind that a number of most competent observers have examined the sections in question, and have arrived at conclusions directly opposed to those announced by the officers of the Geological Survey. When, therefore, our author, still speaking of this question of the contemporaneity of man with the glacial epoch, goes on to exclaim: Perhaps we cannot prove it, but there is nothing improbable in the hypothesis, and I am not the only one who believes it," we cannot help entertaining the feeling that this is hardly the spirit in which a scientific question should be treated, and that the method which he adopts is one scarcely calculated to carry conviction to the mind of any competent judge of the matter. In laying down this book we cannot refrain from once more expressing our opinion that it is a work of the highest value, and one worthy to take a foremost place among popular manuals of science. The illustrations are excellent; the woodcuts, by Mr. Sharman-giving a very faithful representation of species which have been selected by Mr. Etheridge as characteristic of the several formations are quite new, and some views of scenery have also been added to those contained in former editions of the book. The little geological map of Great Britain, which we are glad to see reproduced, is a marvel of clear and accurate printing in colours, and well sustains the reputation of the publishing firm which has produced it. FLORAL DIAGRAMS Blüthendiagramme. Construirt und erläutert von Dr. A. W. Eichler, Professor der Botanik an der Universität Kiel. (Leipzig: W. Engelmann. Theil i.,.1876, Theil ii., 1878.) THI HIS book supplies a want that every real student of systematic botany must have felt. The introductory chapters are devoted to an inquiry into the morphology of the flower and its parts, and the inflorescence; while the subsequent chapters are a full exposition under the head of each family and order of the floral type and its most important modifications. Preceding each order is a list of the most important works bearing on it, and every quotation is accompanied by a full reference. Hence the book is both a Thesaurus of the literature of its subject, and moreover a Prodromus of phanerogamic morphology. Despite the modest title, the vegetative arrangements are explained wherever they present interest, and the same ungrudging pains are often extended to fruit and seed. Unlike too many authors Prof. Eichler is utterly free from provincialism. He cites as freely and constantly foreign botanists as those who have used the German language. Unfortunately we are but poorly represented, for morphological research is all but unknown in England, and is untaught by both our swarms of botanical lecturers and the great institutions which are the outward and visible sign of what Government recognises as botany. The medical curriculum has overborne original teaching by the former, the herbarium has stunted all else in the latter. Hence few of our botanists are able, like an Eichler or a Baillon, to check observations on the adult flower, with its parts distorted by drying and soaking, by their own knowledge of the growth of the living plant. Even the greatest sagacity and experience must be at a loss sometimes from this weakness in the very foundations of their work. For this reason one regrets the more that Eichler makes not a single reference to the works of Griffith, perhaps the greatest botanical genius England ever possessed, who found out for himself the value of developmental research and worked out many a flower by its aid. A word on the method of Eichler. The actual editor of the "Flora Braziliensis," he adds to his thorough knowledge of morphology proper a rare acquaintance with systematic botany. Hence he belongs to no school, though awake to the value of workers in more limited fields, in all of which he himself has done good service. A firm evolutionist, he accepts the testimony of systematist, anatomist, teratologist, organogenist, and histogenist, and believes that all of these can in turn shed light on doubtful points. Hence his opinion must be respectfully considered by those who differ from it, and it is worth while to note a few of his conclusions. cases. He regards the nature of the "calyx tube" as varying with the order; truly receptacular in Rosaceæ, for instance, it is, partly at least, appendicular in some The petals of Primulaceæ are regarded as true petals, and not as appendages of the stamens, a view which our descendants will have forgotten or unearth with the lazy amusement with which we look on some of the naif theories of our ancestors. The nature of the placenta and ovule is a more difficult question, and our author, who, in the preliminary chapters of Part i., published in 1876, held it essentially variable, has been led chiefly by Celanowsky's arguments to regard it as in all cases an outgrowth from the carpellary leaves. Similarly, the ovule, regarded in the First Part as a bud, is now viewed as an emergence. Of course the last word is not yet said on these points, but it is worth noting that Warming also avows his final conversion by Celakowsky, in his brilliant paper on the ovule in the first volume of the Annales des Sciences Naturelles for 1877; and Eichler is at one with Warming in adopting Brown's view of the female flower of Gymnosperms. It is much to be regretted that this point was not really discussed at the late congress in Paris, or that its principal advocates do not answer the latest arguments in its favour. But the question cannot at all be regarded as settled. The cup of Euphorbia is regarded as an inflorescence; but though the pros and cons are fairly stated, no new light is shed on the matter. Enough has been said to show the extreme value of the book to the scientific botanist. May its teachings quicken sound study in England. MARCUS M. HARTOG OUR BOOK SHELF Manuel du Voyageur. Par D. Kaltbrunner, Membre de la Société de Géographie de Genève. (Zurich, J. Wurster und Cie, Editeurs. Paris, C. Rheinwald und Cie, 1879.) A GREAT difficulty of writing a treatise for the use of travellers, on "What to Observe," lies in the impossibility of presenting to the imagination an ideal average traveller to address. If the great mass of intending travellers had much the same amount of scientific knowledge and were well grounded in the elements of science generally, a very useful and compact work might, no doubt, be composed. But as a matter of fact such persons are usually very ignorant, or variously ignorant, and a book fitted to instruct the whole of them must omit none of the more elementary considerations, and therefore would assume the shape of a collection of encyclopædic treatises. It is hard to define the level of previous knowledge to which "Kaltbrunner's Manuel du Voyageur" is best adapted. Every reader is sure to think it too diffuse for his own wants in some parts, neither deep nor full enough in a great many, and probably beyond his depth in others; but take it all in all, it is perhaps better adapted for persons of moderate culture than any similar book that could be named. It is beautifully got up, with abundant illustrations, and to say the least, would be often useful for reference and as a reminder. The range of its topics is wide enough to touch the interests of everybody, and it would be a capital present to give to a friend bound for foreign parts. Considerable space is allotted to subjects connected with social life and other anthropological questions. There seems to be some irony in the fact that when the world is so nearly explored, manuals for the use of travellers should begin to appear. They were greatly needed many years ago, when the Admiralty Manual had the field nearly all to itself, but now that the need is less, these works are at last composed in abundance. The present one, however, is by no means intended to supply the wants of those travellers only who are exploring unknown countries, much of it being applicable even to home districts. It is less solid and more comprehensive than the recent German publication, "Anleitung, &c.," by Neumayer. no one, I think, would believe so ill of his fellow-men as to suppose for one moment that advantage could be taken of the sympathies which have been aroused by the Indian famine, or which may from time to time be excited by the record of great disasters by sea and land, to advocate bottomless schemes merely for purbelieve that those who advocate the erection of new We must now, perforce, poses of personal advancement. observatories and laboratories for studying the physics of the sun have the most thorough faith in the scheme which they proffer (p. 51). From p. 194 I gather that I know nothing about the motion of waves, and p. 240 proves me equally ignorant of voltaic electricity. I cannot read any more. P. G. T. LETTERS TO THE EDITOR [The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts. No notice is taken of anonymous communications. [The Editor urgently requests correspondents to keep their letters as short as possible. The pressure on his space is so great that it is impossible otherwise to ensure the appearance even of communications containing interesting and novel facts.] Receiving Telephones I HAVE roughly tried two experiments which seemed likely to supply new forms of receiving telephones, and have had such partial success as seemed satisfactory in preliminary trials. As I have not time to continue the experiments I request the insertion of this note in the pages of NATURE, in the hope that some one else will follow the matter up. In one experiment a spiral wire (I used German silver, but it may be of any material) was wound closely so that the spires were in contact, or nearly so. One end of the spiral was fixed and the other end attached by a thread to the middle of a small parchment drum-head, such as is sold by the toy-makers for thread telephones. A slight tension was put on the thread to draw the spires of wire slightly asunder. The spiral wire was then made part of a circuit, including one or two cells of Grove's battery and a line wire going to another room. By this apparatus such sounds as the scraping on a file were satisfactorily long. It will be observed that in this arrangement there are no heard, although the spiral was only one coil of about an inch magnets; the whole effect is produced by the varying induction of the current upon itself. The apparatus could obviously be rendered more efficient by using a longer spiral, or a coil consisting of a number of concentric spirals not quite in contact, so as to allow small motions to exist. The induction might be Pleasant Ways in Science. By R. A. Proctor. (London: still farther increased by using a spiral of two wires, so that a Chatto and Windus, 1879.) Or this book, which has been sent me for review, I can truly say that it is an excellent specimen of what has been well called (I forget by whom) Paper Science. A very few quotations will amply justify this verdict. At pp. 8, 152, I find "heat" several times standing for "temperature." But the author (in these columns, vol. xvi. p. 227) insisted that "What_mathematicians call the moving force exerted by the earth on the moon is eighty-one times greater than the corre sponding force exerted by the moon on the earth." To put "heat" for "temperature "" is after all not very strange for one who puts moving force" for accelerating force." 66 In the account given of the experiments of Andrews and Tait on ozone, the action of "iodine" is given as that of "mercury" and the now-received idea of the nature of ozone-though_twice mentioned in the paper referred to-is described as a "beautiful" and "ingeniously conceived" hypothesis suggested after the publication of the paper (pp. 351-2).. The following passage, which refers to friends of my own, I quote without comment : powerful local current might be kept up in the alternate spires, while the varying line-current is passing through the intermediate ones. Another improvement would consist in using sation of this coil would co-operate with the electric induction to iron wire wound in a sufficiently loose coil. The self-magnetiheighten the effect. In the other arrangement an iron or steel spiral (in my experiment it was an ordinary steel spiral spring, of which the spires lay close) was placed inside a coil of copper wire in circuit with a battery and the line. The spiral, as before, was fixed at one end, and kept slightly stretched by a string connecting its other end to a drum-head. In this arrangement no current passes through the spiral, but it is the core of an electro-magnet, and becomes magnetised in a degree which changes with the alterations in the intensity of the line-current. This causes the spires to attract one another with varying intensity, and the tremulous motion so produced is propagated by the string to the parchment. By this arrangement singing, whistling, &c., were heard when a Reiss transmitter was used. Probably a soft iron coil would have been better than the steel spring I used, and the apparatus is susceptible of other obvious improvements which would add to its sensitiveness. Before concluding permit me to thank Prof. Barrett for allowing me to make the experiments in his laboratory. Dublin, November 25 G. JOHNSTONE STONEY The Microphone for Military and Tonometric Purposes My attention has just been called to a paper on the microphone, by Prof. W. F. Barrett, in NATURE (vol. xix. p. 12), in which it is asked whether the latter "has ever been tried by military men to detect the mining operations of an enemy?" Will you allow me to state that this application of the microphone suggested itself to me many months ago, and that I have begun to make experiments both in this direction and also with a view to ascertain to what extent sounds can be transmitted to a microphone immersed in water. Unfortunately the pressure of other matters has hindered me from completing the work, which, however, I hope shortly to be able to do. May I take this opportunity of saying that I have been endeavouring with some success to apply the principle of the microphone to the counting of the beats of two slightly dissonant tuning-forks. In one experiment the two forks were inverted and screwed through a board above which the ends of their stems protruded. A thin piece of carbon was laid over these ends and the arrangement was placed in circuit with a Bell telephone. The beats were loudly heard and continued audible long after their direct sound had ceased. A reflecting galvanometer being placed in the circuit the beats were shown by deflections of the light spot, but irregularities in the current made it difficult to count them satisfactorily. The forks were then screwed horizontally into a vertical board and a screw was inserted about I" from the stem of each and on the same horizontal level. A small piece of carbon was laid over each stem and its adjacent screw. This plan gave even better results, and admits of the forks being any reasonable distance apart. The experiments were tried with two forks whose vibration numbers were about 60, and also with a pair of octave forks with vibration numbers of about 256 and 512. A small piece of copper wire was then attached to each of the two large forks, and mercury cups were so placed that the points of the wires were just not touching the mercury surface when the forks were at rest. Both mercury cups were connected to one pole of the battery, and the current was arranged to branch through the forks uniting at the telephone. The beats were very loud. This plan, however, involves difficulties on account of the delicacy of adjustment required for the mercury surfaces and also the amalgamation of the copperpoints. Several other experiments have been tried, but the method first described seems worth a trial by those interested in tonometry. The counting of beats, which is not an easy matter for aged or unaccustomed ears, may thus be immensely facilitated, while the period of the forks under observation is absolutely unaffected. The carbon used was that employed for the electric light, and it is probable that more carefully prepared and homogeneous material would have given better results in a galvanometer experiment. GEORGE S. CLARKE Cooper's Hill, November 19 The Microphone as a Receiver ON the 3rd of June last, in a paper read before the Royal Society of Edinburgh, I described an experiment which showed that the microphone could be used, not only as a transmitter, but also as a receiver of articulate sounds. An abstract of the paper appeared shortly after in NATURE, and since then I have had communications from several experimenters, stating that they had failed to repeat the experiment, and asking for some details regarding it. I trust, therefore, that you will kindly give me space for a short explanation. In performing the experiment the transmitting and receiving instruments which I used were precisely identical. Each was merely an ordinary white porcelain jam-pot, 3 inches in diameter and 4 inches deep, half filled with gas-coke, broken into coarse fragments and provided with electrodes whereby a current of electricity could be sent through the pieces of coke. Cinders from ordinary coal, if well burned, would, of course, do equally well. The electrodes were two strips of tin about two inches wide slipped down, opposite to each other, between the cinders and the sides of the jam-pot and fastened by being bent over the edges and bound round the outside with a cord. When these jam-pots were put in circuit like a pair of ordinary telephones, and a battery of two strong Grove's cells, or four ordinary Bunsen's, included in the circuit the arrangement was complete. In this way I have had no difficulty in making myself and others clearly hear the transmission both of singing and speaking, although, as I stated in my paper, the articulation is not so dis tinct as I have no doubt it will be when proper forms both of transmitter and receiver are adopted. greatly improved by including a stronger battery in the circuit. Wind-Pressure larly great wind-pressures registered at the Liverpool ObserI BECAME acquainted, some years since, with the singuvatory, and I should be rather disposed to attribute them to the exceptional position of the wind-gauge than to think (as the writer of an article in NATURE, vol. xix. p. 25, appears to do) that the gauge is erroneous. I do not remember to have seen it noticed, in the recent discussions on the Cleopatra's Needle, that there is probably a rapid increase of wind-pressure from the ground-surface upwards. In any river the velocity is least at the bottom, and near the bottom the change is rapid. Similarly, in the great current formed by the wind, I imagine there is a much less velocity near the ground than at some distance above it, and less on a plain than above a hill standing out of the plain. Now I believe the Bidstone Observatory is on a hill, with the great plain formed by the Atlantic in front of it. It is, therefore, in a position in which it receives an exceptionally heavy wind-pressure. The pressure on the wind-gauge is probably much greater than on the windows of the observatory, ings more inland, where the current near the ground has been and that, again, is probably greater than the pressure on buildmore interfered with by obstructions. On the other hand, Cleopatra's Needle is in a very protected position, where I should be much surprised to find that the wind-pressure ever reached even 40 lbs. per square foot. = As Mr. Dixon has referred to the case of a window to disprove the possibility of a pressure of 80 lbs. per square foot, it may be well to see whether it is really conclusive. I have not at hand any formula for the resistance of a simply-supported square plate, but it will not be very different from that of a circular plate. Now, let p = pressure per square inch on surface of plate, its thickness, r its radius. Then the greatest stress 5 in the plate is by Grashof's formula, f.. Taking a plate of glass 2 feet diameter,inch thick, and loaded with 80 lbs. per square foot, we get f=4,270 lbs. per square inch. In some experiments which I made under Sir W. Fairbairn's direction, the tenacity of glass was found to be from 4,200 to 6,000 lbs. per square in. Hence, surprising as it may seem, it is probable that a pane of glass 2 feet diameter would sustain a load of 80 lbs. per square foot, uniformly distributed, without breaking, or a load equivalent to that of a dense crowd of people. I don't, of course, think that a window would be safe if subjected to such a pressure, but it is always desirable to subject general statements of this kind to exact calculation; and I think we may at least infer that well-constructed glass windows would sustain a considerable wind-pressure without necessarily giving way. W. C, UNWIN Cooper's Hill, November 17 Was Homer Colour-blind? I CRAVE Some little space for a few remarks with regard to the recently much vexed question as to the traditional blindness of Homer. It seems to have been overlooked that, apart from the statement made by Herodotus (in his life of Homer), that in Homer, according to Herodotus, was born about 167 years after the Trojan war and, when still a child, adopted by his stepfather, to whom he succeeded in the management of a school. At an early age, however, it would seem, he set out for distant voyages and, at length, after having spent some time on visiting Tyrrhenia and Iberia, when about 32 or 34 years of age, lost his sight from what appears to have been some chronic disease of the eyes. Previously, when at Ithaca, he is said already to have had a narrow escape from that calamity. The text of this important narrative runs thus :— οἱ μὲν Ιθακήσιοι λέγουσι, τότε μὲν παρ' ἑαυτοῖς τυφλω θῆναι, ὡς δὲ ἐγώ φήμι τότε μὲν ὑγιῆ γενέσθαι, ὕστερον δὲ ἐν Κολοφῶνι τυφλωθῆναι ; συνομολογοῦσι δὲ μοι καὶ Κολοφώνιοι τούτοις Απικομένω δὲ ἐς Κολοφῶνα συνέβη, πάλιν νοσήσαντα τοὺς ὀφθαλμοὺς μὴ δύνασθαι διαφυγεῖν τὴν νόσον, ἀλλὰ τυφλωθῆναι ἐνταῦθα. Ἐκ δὲ τῆς Κολοφῶνος τυφλὸς ἐὼν ἀπικνέεται εἰς τὴν Σμύρναν . . From Colophon he sailed to Smyrna, where, for his sustenance, he began and, afterwards, continued, during his long wanderings, and for a good many years, the recital of his verses. ἱππότε κέν τις ἐπιχθονίων ἀνθρώπων ἐνθάδ' ἀνείρηται ξείνιος ταλαπείριος ἐλθών If some day an earthborn man, a wayfaring stranger, Whose songs are, oh lasses, the most delightful to you, It is the blind man who dwells in the rocky island of Chios, I need not add, as a further argument, that Homer frequently was alluded to as the blind and humpbacked man, å kupòs kal Tupads dvnp,1 and it seems to me trifling to qualify, or mitigate, the racy juxtaposition of the two epithets. To what extent colour hallucinations, so frequent in connection with certain forms of blindness, may possibly have impaired the poet's imaginative faculties with regard to the varying hues and shades of colour, it would be for the present, from want, for obvious reasons, of similar observations, difficult to settle. However, I cannot but think that what by some so recently has been called Homer's colour-blindness may be the natural consequence, on the one hand, of the increasing dimness of his recollections as well as owing to these optical hallucinations, and finally, to the defective chromatic terminology of his time. The following are some of the Greek and Latin authors who, together with Herodotus, aver and enlarge upon the blindness of Homer :Plutarch, Vita Hom. 12; Thucyd., III. 104; Pausan., II. 33, 3; III. 4, 33; Lycophron, Cassandra, 422; Aristot., Orat., L. p. 703; Cicero, Tuscul, V. 39. I refrain from discussing the question whether, from a physiological point of view, such a profound functional perturbation as is involved in the term of colour-blindness, viz., deficiency in the perception of any plurality of colours in the spectrum, would not seem to be symptomatical of most momentous organic disturbances in the nervous apparatus of the eye, generally conducive to the most hopeless forms of blindness. Scientific Club J. HERSCHEL IN reading Mr. Pole's article on Homer's sensations of colour, there is one point which seemed to me to call for explanation. Mr. Pole says that in the solar spectrum he sees only two colours, blue and yellow, and that the red space appears to him yellow. From this one would naturally infer that the whole of the spectrum visible to ordinary persons is visible to him also, but that it presents only these two colours, which graduate into one another without any break, and that the green space appears as yellow. And with a colour-blind person who has allowed me to test his capabilities, I found this actually to be the case. But later on Mr. Pole says that pure red and pure green appear to him not yellow but grey. I would wish, then, to ask Mr. Pole whether the spectrum presents to his vision, in place of the green, a neutral space or an interval of darkness? In other words, have the rays of that particular refrangibility no action at all upon his retina, or is it that they have no action peculiar to The very word of"Oμnpos signified “blind" in the vernacular idiom of Kúμn, or Cumæ, one of the Eolian colonies in Asia Minor, where he lived for some time, and, as will be shown anon, accidentally came by the name of Homer, his original name being Melesigenes, from his happening to be born on the banks of the small river Meles, which flows by Smyrna and runs into the Smyrnian sinus. One day, pointing out how much of the poet's glory was certain to redound to their own city's glory, if the poet could be induced to settle among them, it was proposed to the people of Cuma to provide during his lifetime for his wants, at the public expense, when somebody explained that such a resolution would be tantamount to inviting all sorts of blind," Ounpol, and useless, people to their city, whereupon the proposal dropped. But it seems that, henceforth, the poet went by the name of Homer: Ὅμηρος ἐπεκράτησε τῳ Μελησιγενεῖ ἀπὸ τῆς συμφορῆς ; οἱ γὰρ Κυμαῖοι τοὺς τυφλοὺς Ὅμηρους λέγουσιν. Ωστε πρότερον όνομαζομένου αὐτοῦ Μελησιγενέος, τοῦτο γενέσθαι τοΰνομα Όμηρος. Herodot. Halic., vita Hom., 2, 13. themselves, but simply produce the general effect of light? In either case the phenomenon seems more anomalous than if he saw all colours as colours, though he could only class them under two heads. To take a familiar analogy, it is as if a man should be perfectly able to distinguish the pitch of notes at either end of the scale, but the notes between should either not affect the auditory nerve at all, or should affect it simply as noise. Pembroke College, Oxford FRANK PODMORE Anthropometry As I have stated in the preface that my object in publishing my "Manual of Anthropometry" is to invite criticism with a view to perfecting the anthropometrical chart which it contains, and which forms its chief feature, I may be excused for referring to the notice of the work which appears in NATURE, vol. xix. p. 29. The reviewer objects to the large number of measurements given in the chart, but he has overlooked my statement that many of them are of a secondary character, and that I leave the student liberty to select the measurements which best suit his recorded in a uniform manner, and thus become the common purpose, requiring only of him that they shall be made and property of statisticians. Anthropometry can make no progress as a science, so long as observers are at liberty to make the same nominal measurement of the body in four or five different ways, as is the case, for instance, with chest-girths. I may add that my manual was not written for the three or four individuals in this country who have mastered the "theory of human proportions" as a mathematical curiosity, but for army surgeons, busy medical men, schoolmasters, and others who are much more concerned with actual facts than theories of probabilities. CHARLES ROBERTS Bolton Row, W. Divisibility of Electric Light IN all communications on this subject in NATURE and elsewhere, the division of light is considered only with reference to parallel circuits, and this naturally causes great loss of light by the law that heating is proportional to the square of the current. But in electric circuits their resistance has always to be considered; and if two lamps are taken parallel, only half the resistance of the one lamp is obtained, and such resistance can be obtained by taking two parallel circuits of two lamps in series in each; the light obtained then is one quarter in each lamp, as half the current is flowing through each circuit, and as four quarters make a whole, no loss of light is caused by division in such a method of one current to any number of lamps. There are certainly practical difficulties in the way of burning lamps in series, though these are greatly diminished if incandescent wire is used as the light-emitting source. However, there is no inherent reason why the electric light should be wasteful in division, as is described by Mr. Trant. F. JACOB Verification of Pervouchine's Statements regarding the Divisibility of Certain Numbers THE statements of Pervouchine, reported in some recent numbers of NATURE, are equivalent to the following :-That the 210 power of 16 is less by 1 than some multiple of 7 x 214+ I ; and the 221 power of 16 is less by I than some multiple of 5 X 225 +1. of rn Let be the remainder after dividing the 2o power of 16 by one of the above divisors. Then since the 2+1 power of 16 is the square of the 2n power, +1 differs from the square by a multiple of the divisor; or +1 is the remainder arising from the division of the square of Use for the work the scale whose radix is 16. In this scale the above divisors are I 12 O O I and IO 0 O O O O I. In the first case, calculating on the plan indicated, we find the remainders. |