recommendation. We believe the author has omitted by far the most important reason, viz., the deposit of heavy road detritus caused by the admission of storm waters, which retards the free flow of the sewage and retains a mass of decomposable matter in the sewers quite sufficient to account for the abominable effluvium emitted by the gullies and ventilators of the London system. A reason advanced for the admission of surface water into sewers given by the author, and to which much weight is attached, is the fact that it was found by the analyses of Prof. Way that the washings from the streets of London resulting from rainfall were equal in impurity to average sewage. If the surface of our streets is permitted to become so filthy that, even when diluted with rain-water, the product is only suited for admission into the sewer, it would surely be better to turn more attention to the collection and carting away of the filth rather than to get it washed away out of sight where its presence will not be remarked until the next dry weather renders it painfully apparent. It is somewhat to be regretted that the author has not devoted a small amount of space to a subject having so important a bearing on the sanitary condition of a town and the successful operation of a system of sewerage as the scavenging of streets, especially when we consider how much improvement in this respect is needed in the metropolis. We believe that in London and other large towns, the saving in the destruction of clothing would at least pay for the proper cleansing of the streets without making any allowance for the saving of time and discomfort in locomotion.

The chapters dealing with the properties of materials and the construction of sewers, contain much useful information derived from the author's own experience and other sources, and may be consulted with much advantage by those engaged on works not only of this, but of other descriptions.

The much vexed question of sea outfalls and the influence of tidal currents on the selection of site is discussed, but it seems a pity that where ignorance and prejudice demand this mode of disposal, the author should not have laid stress upon the necessity of abstracting much of the solid matters held in suspension, thus much diminishing what is becoming an intolerable nuisance in many sea-side places. In giving so much importance to dilution with tidal water, it should have been borne in mind that this takes place in the direction of the breadth and depth of the volume of liquid discharged; but in the case of the solids floating on the surface, only in the former direction, and in both cases very slowly, as may be seen by an inspection of the metropolitan outfalls. It is impossible in the space at our disposal to notice the numerous details described and illustrated; the plates of all the more important are carefully drawn and well executed, no trouble being spared to make them thorough working drawings, while a sufficient number of woodcuts are introduced amply to illustrate the text. There are other books on this subject of a more popular nature, containing most of the information required by those who desire a general knowledge of the subject freed from too technical matters, but this is undoubtedly the best book hitherto published in this country for the student of practical sanitary science and for the engineer who requires a thorough treatment in detail of that branch of his practice.

THE NAPLES ZOOLOGICAL STATION

Mittheilungen aus der zoologischen Station zu Neapel, zugleich ein Reperatorium für Mittelmeerkunde. Erste Band, I. Heft. (Leipzig: 1878.)

INCE the foundation of the Zoological Station at

SIN

Naples, nearly one hundred naturalists have worked in the laboratory connected with it, and a goodly number of papers, which have resulted from their labours, are scattered through the biological periodicals of almost all the civilised nations of Europe. Gratifying as this success must be to Dr. Dohrn, the founder of the institution, he does not show himself inclined to repose on his laurels, but aims at still further extending the scope of the station by starting two publications in connection with it. One of these, of which we have the first number before us, is published in octavo size, and, as we learn from the preface, is intended for smaller papers, and general notes on the habits of animals living in the Aquarium, and other zoological topics. It will, moreover, be the medium for recording the systematic observations now being carried on by the permanent staff at the station. The second publication will be in quarto size, and will bear the title "Fauna u. Flora des Gulfes von Neapel und der angrenzenden Meeresbezirke." As its name indicates it will consist of fully illustrated monographs of the various groups of animals found in the Bay of Naples or adjoining seas. The parts may be purchased separately, or may be subscribed for by the payment of 17. yearly. The contents of the first part of the "Mittheilungen" promise very well. Dr. Schmidtlein, who manages the public aquarium, contributes three short papers. One of them gives an interesting account of the habits of a large number of the various animal forms living in the aquarium. A second deals with the periodic appearances of pelagic animals in the Bay of Naples during the two past years, and the third is a list of the breeding times of the marine forms inhabiting the Neapolitan seas. Dr. Hugo Eisig, the general manager of the station, contributes a paper of very great importance on the segmental organs of the Capitellida. He shows that, in some species of this group, it is normal for several segmental organs to be present in a single segment, and that the number of these organs present in a segment increases in passing from before backwards. Dr. Eisig compares the segmental organs in Annelids with the segmental tubes in Vertebrata, and points out how closely the arrangement he has found in the Capitellidæ agrees with that described by Dr. Spengel in some Amphibia. There is an illustrated paper by Dr. Meyer on some points of crustacean anatomy, and two botanical papers by Drs. Falkenberg and Smitz. Dr. Dohrn himself communicates some observations on the Pycnogonidæ, in which he adduces a large amount of evidence to prove that the view as to the number of their appendages put forward by him some years ago, which was subsequently attacked by Semper, is, in all essential points, correct.

The number as a whole is very creditable to the zoological station, and we may congratulate the founder upon the continued prosperity of the institution, as evinced by its ever-increasing activity in all directions.

F. M. B.

OUR BOOK SHELF

Theorie der algebraischen Gleichungen. Von Dr. Jul. Petersen. xii. and 335 pp. (Kopenhagen, 1878.) THE author tells us that this work owes its origin to the lectures he has given on the theory of equations at the Copenhagen Polytechnic School. In the preparation of it he has made use of J. A. Serrêt's "Cours d'Algèbre Supérieure," Todhunter's "Theory of Equations," and Jordan's "Traité des Substitutions." The first section treats of equations in general; Cap. I. general properties of algebraic equations; Cap. II. relations between the coefficients and roots; Cap. III. on elimination, describing the methods of Labatie, of Euler, of Sylvester, of Bezout, and of Poisson; Cap. IV. the transformation of equations. The second section is devoted to the algebraic solution of equations, viz., of the cubic (the methods of Hudde, Lagrange, Tschirnhausen, and Euler); of the biquadratic (the methods of Lagrange, Descartes, and others); the binomial equation, the Quintic, the breaking-up of a rational polynomial into rational factors, Abelian equations (a long chapter, including the division of a circumference into seventeen equal parts, and the reduction of the equation r13 = 1).

The third section is on the Numerical Solution of Equations: Cap. I., on the Separation of Roots (Descartes', Budan's, Rolle's, Sturm's, and Newton's theorems); Cap. II., the Calculation of the Roots in Numerical Equations (interpolation, of Newton's Method of approximation, also Lagrange's and Horner's methods). The fourth part, which treats of Substitution in four chapters: Cap. I. Substitution in General; Cap. II. (a long chapter, including the theorems of Lagrange and Cauchy, alternate, transitive, and intransitive groups, linear substitutions, &c.); Cap. III. Galois' Theory (this has not found its way into English text-books; Prof. H. J. S. Smith classes Galois, for early precocity, with Pascal and Gauss); Cap. IV. Applications of Galois' Theory (Abelian equations, the Galois and the Hessian equations).

This bare enumeration of the principal articles will show that this carefully-written treatise takes up some ground which has not yet been opened out or even alluded to in our common text-books on equations.

By

The Botany of Three Historical Records, Pharaoh's
Dream, The Sower, and the King's Measure.
A. Stephen Wilson. (Edinburgh: David Douglas,
1878.)

THIS is a curious little book, the author's aim being to throw what light he can, either by comparison or suggestion, upon the probability of the plants referred to in these Scripture records being this or that species of cereal. Mr. Wilson seems to have given a good deal of consideration to each of the above questions, which, as he says in his preface, have only one bond of connection between them, namely, "a common basis in the botany of the cereal grasses." Notwithstanding the pains the author has evidently given to each of the subjects, we cannot but think that it will prove of but little value, the points advanced being by no means conclusive, and even the subjects in themselves being of small importance. It may be of some value to know whether the cereals "stand in the same alimentary relationship to mankind as they did when Joseph laid up the surplus of the plenteous years in the granaries of Egypt," because such a knowledge, if it could be proved, would show the progress made in developing the productive resources of these grasses, but whether the plant in Pharaoh's dream was Triticum compositum, or any other species of Triticum, is perhaps of little moment to mankind at the present time. As an illustraiton of what is to our mind mere speculation, we quote the following from p. 6:-"The wheats of Minnith,' in the

Belka (Ezek. xxvii.) grown by the farmers of Judah and Israel, seem to have been in demand in the cornmarket of Tyre. Probably Minnith was a remarkably good locality for wheat, so that when the husbandman in other districts got seed from this place they called it Minnith wheat."

The author's summing-up of this his first "Historical Record," namely, that " seven ears of corn came up upon one stalk," is that it " may be wrong, and probably is wrong, whereas the reading here proposed, that seven ears of corn came up upon one stock, while probably expressing the full meaning, can only err by defect, and must necessarily be right, as embracing an essential morphological fact common to all varieties of corn." The Commercial Products of the Sea; or, Marine Contributions to Food, Industry, and Art. By P. L. Simmonds. With thirty-two illustrations. (London: Griffith and Farran, 1879.)

THIS is the first example this year we have had of a work antedated, in this case by more than two months. We cannot possibly see what is gained by this; is it meant to make readers of future years believe that a work was published a year later than it really was? If this is so, is it quite honest and respectable-to put it in the mildest possible form? When one gets over Mr. Simmond's extraordinary and often misleading style (for which we commit him to the tender mercies of the literary Dr. Birch), it is found that his work contains a great mass of useful and curious information, showing great diligence in the collection of facts, if not much skill in putting them together. Mr. Simmonds' work is divided into three parts, dealing with food-products obtained from the sea, marine contributions to industry, and marine contributions to art. Detailed accounts and statistics are given of the various fisheries of the world, under the first head; under the second head the sponge fisheries are dealt with, oils, isinglass, shells, seaweed, marine salt, and other products; and under part iii. tortoise-shell, mother-of-pearl, coral, and amber. It will thus be seen that the work has a wide range; it shows how much has been done, and how much yet remains to be done by science, to make the most of the products with which the waters swarm. gether the work contains much useful and interesting information in a handy form.

Alto

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.]

A Question raised by the observed Absence of an Atmosphere in the Moon

It is known that there is physical evidence of an absence of atmosphere in the moon. It would appear reasonable to conclude that the moon at one time had an atmosphere; for, according to the generally-accepted principles of Laplace, which make the sun and members of the solar system to have a common nebulous origin, it would seem very extraordinary if the particular offshoot of the common nebula which formed the mon

set.

velocity, i.e., a velocity to which apparently no limits can be It is true that the molecules which in the accidents of collision among themselves acquire these enormous velocities, have been mathematically proved to be relatively few in number, the greater number of the molecules possessing velocities approaching the mean value. But it would seem to follow necessarily that molecules situated in the top stratum of any atmosphere, and which acquire these enormous (indeterminable) velocities, can sometimes overcome gravity, and be projected into space, so as not to return; as it is a known fact that only a finite velocity is required to effect this result. I have therefore to suggest that by this cause the moon's atmosphere has gradually disappeared. It is probable, no doubt, that it would take a vast period of time to have brought about this result, but we have an almost unlimited time at disposal. It might possibly be asked, How is it that the earth's atmosphere has not shared the same fate? In answer to this I would reply, first, that the value of gravity on the earth is known to be very much greater than on the moon, and second, that possibly (for aught we can tell) part of the earth's atmosphere may have thus disappeared; or the earth's atmosphere may be less dense at present than at one time, for anything we can say to the contrary. It would seem a curious fact to note in connection with this that there would be apparently grounds for inferring that the constitution or composition of the earth's (or any other planet's) atmosphere might have changed from the above cause, as evidently the lighter gaseous constituents, whose molecules acquire in the accidents of collision the highest velocities, would be first dissipated into space in the above manner. Thus, for example, any trace of that very prevalent constituent of the universe, hydrogen, that might have at one time existed in the earth's atmosphere, would have tended to become relatively rapidly eliminated, as the molecules of hydrogen are known to possess a normal velocity about four times as great as that of the constituent molecules of the earth's atmosphere. It might be said that changes so great as those above indicated are scarcely realisable, but then it should be kept in view that we have an almost limitless range of time to draw on, and it is generally admitted to be very important to take the effect of time into due consideration, as, for example, is done in the case of geology, where mountain ranges are recognised by incontrovertible physical proof to have been carved out by the slow disintegrating action of rain and atmospheric influences prevailing through countless centuries. The gradual disappearance of an atmosphere (earth's or moon's) under the above cause might possibly be compared in slowness of operation to the other cosmical changes that the solar system is known to be undergoing, such as the gradual approach of the earth to the sun (and of the moon to the earth) through the friction of the material media in space, the accomplished stoppage of the moon's axial rotation by tidal action on its mass, and the gradual diminution of the earth's rotative velocity from the same cause. These slow changes, imperceptible in the range of human experience, become important in large time epochs, and it becomes desirable in the interests of truth, in tracing back events, to give due weight to these time epochs. In suggesting the above explanation, I have endeavoured to confine myself strictly within the limits of mathematically proved facts as a basis to draw deductions upon, and I should be glad to accept any criticisms that might be offered, either with the view to point out a difficulty or confirm the truth. London, October

S. TOLVER PRESTON

Remarkable Local Colour-variation in Lizards THE following extract from a letter received some months since from Baron de Basterot, of Rome (a Fellow of the Geological Society of London), records an interesting case of local colour-variation, about which some of your correspondents may be able to give us further information :

"Capri is a mass of the usual yellowish-white Apennine limestone, forming precipitous cliffs nearly all round the island.

The realisation of a possible diversity at a former epoch in the constitution and density of the earth's atmosphere raises rather a curious question in connection with the known diversity of the plants and animals that formerly inhabited the globe, as compared with those at present existing. It might be observed that admitting the possibility of the former existence of an atmosphere on the moon, it would seem to follow that an interchange of molecules between the two atmospheres (those of the earth and moon) must have taken place at one time to a certain extent under the above cause, though the considerably less value of gravity on the moon compared with the case of the earth would facilitate the passage of molecules away from the moon and render correspondingly difficult the passage in the reverse direction.

At its southern extremity are three high and nearly inaccessible rocks called I Faraglioni, one of which, pierced by a natural arch, has been frequently depicted by artists. Two of these rocks are completely detached from the mainland, and, I need hardly add, uninhabited.

"On the island, and on the first of the Faraglioni rocks which is connected with it, the lizards are of the usual species so common in Italy-coloured grey, mixed with more or less green. On the two outward Faraglioni rocks, which are completely separated from the shore, their colour is totally different. The back is of a blue so dark as to appear nearly black; the sides of a brilliant blue, like lapis-lazuli; the belly light whitish-blue, with a very slight tinge of green.

"An English gentleman whom I met in Capri had several of these lizards alive, which had become quite tame in the course of a couple of months. I believe he intends bringing them to England. He is of opinion that they differ in colour only from the lizards of the island, and that, though very different in appearance, they are the same species.

Whether this be so, or whether they are specifically different, their presence on these isolated rocks and their total absence on the island is equally remarkable." ALFRED R. WALLACE

Termites kept in Captivity by Ants

WHEN entomologising in Portugal in 1877, in the neighbourhood of Cintra, I found the nest of Formica nigra under a stone. On my turning it over there was, as usual, great consternation in the community, and I discovered that it was evidently caused by the fear lest a colony of Termes lucifugus, which the Formicas had enslaved, should escape. The Nigras instantly began seizing the Termites, driving them underground by the nearest orifices, in the meantime wrenching and pulling off their wings in the most unceremonious manner. I observed a large number of wings lying in heaps here and there in the nest as if this treatment had been practised before. In the nest there was also a great number of Termite larvæ. The great object of the owners of the "location" seemed to be to get these larvæ underground as speedily as possible. The ants fell on them with great impetuosity, seizing them anyhow and anywhere, dragging them against the most strenuous opposition (their behaviour strikingly contrasting with the meekness of their winged fellows) into the nearest apertures of the underground home. Very often this opposition resulted in a long and stern fight, in which the larvae were often badly wounded, being deprived sometimes of their antennæ, sometimes of half their jaws, and not seldom killed outright. Occasionally, however, the larvae were victorious, beating off the Formicas, in which case they (the larvæ) did not make off, but remained perambulating the nest. I saw one larva drawn at the end of a long fight by its antenna, while it strenuously held on to a small ball of earth which had proved a vain anchorage for its feet, for larva and clod together were dragged across the top of the nest (made by the impression of the stone) five or six inches, up the side, 1 inch, and away among the grass, where, losing the ball of earth, it seized a stalk so firmly that its abductor could not drag it farther, whereupon, after reconnoitring the ground for a little distance the latter disappeared, but returned shortly with a companion, with whose aid the larva was detached. This done, the helper returned home while the abductor proceeded with his prisoner till lost to view in the grass, some twelve or fourteen inches from the spot whence it originally started.

In the same neighbourhood I watched for some time a nest of Formica ligniperda. An injured female was placed in the nest, but no assistance was rendered, while it crawled along towards the nearest orifice leading underground. At the spot where this individual was injured some of the fluid of its body which had oozed out was eagerly lapped up by the others; some even applied their mouths to the wounds on the body. During the operation of lapping the maxilla were kept perfectly still, and the antennæ close to the side of the head "feel-feeling" the ground with the tips, as if to discover the spot where the liquid was to be found. Every now and then, however, they were extended at right angles to the body, as if to obtain a more general survey of things, and then immediately returned to their previous position. On several of those which were busy lapping I poured some spirits of wine. They instantly became stupefied, and for a time motionless. When in this condition they were

visited by many of their fellow colonists, who, having cursorily examined them, fell to touching them with their antennæ on the abdomen, reminding me much of a mesmerist making passes over a victim. The effect was almost electrical. I was surprised to see the incapables at once begin to rally. After stretching their legs and moving their antennæ they moved along slowly for one or two steps and then went along as if nothing had happened. Others came and drank of the spirit not quite evaporated, but did not seem to suffer any bad effects. I buried a member of the community as it was in the act of carrying off a larva. Although many came and looked on none took compassion or attempted to relieve their friend. A small heap of larvæ, however, which I pressed down into the soft earth with my pencil, thereby injuring some of them badly, was disinterred, and every individual carried into a place of safety.

A stranger placed in the nest was very soon set upon, and before long its head was travelling on a direction opposite to that of its abdomen. The headsman's reward was a long draught of

blood from the severed abdomen.

On my turning over the stone at first, the larvae were exposed, but were soon begun to be carried off. Some of the workers were certainly busybodies, fussing about, pretending to do a great deal, while in fact they were shirking their fair share of the household duties. They would rush at the larvae, seize one and be off with it in a great hurry, but they had not gone far (not even always in the direction of the entrance) before they changed their minds, threw down their load to return for another helpless infant, which was treated in the same way, being carried generally in a direction contrary to the previous, and dropped down anywhere, sometimes beyond the limits of the nest altogether.

My observations with regard to ants dropping intentionally or jumping from small heights do not quite agree with Sir John Lubbock's, but they are not yet full enough to give in detail. I hope to have fuller opportunities for the investigation of the habits of this most interesting class in the Malayan Archipelago, whither I am now bound.

Meantime I hope these few notes may have some interest for

the readers of NATURE.

S.S. Celebes, off Naples, October 18

Colour-blindness

HENRY O. FORBES

THE Conclusion of Dr. Pole's valuable paper will doubtless stir up many to investigate the question whether or not dichromatism was the rule at an early stage of human vision.

Will you allow me to adduce, towards the solution of this question, the evidence of a literature, which though not nearly so ancient as the Greek, goes back further than that of many European nations. I mean the Irish. I find in some of the earliest works in that language an ambiguity in the application of adjectives of colour very similar to that noticed in the Homeric writings by Mr. Gladstone. Glas, for instance, is used, indifferently, apparently, for green, grey, and blue. Uaithne is used to indicate the colour of grass, and also that of the human eye. Dearg is employed to denote the colour of wine, and also that of clay. Ruadh (red) is similarly ambiguous. 182, Adelaide Road, N.W.

Carrier-Pigeons

EDMUND MCCLURE

IN NATURE (vol. xviii. p. 682) it is stated that carrier pigeons are being "turned to useful account" in a new direction in Germany, for Consul Ward writes to the Foreign Office "that the successful results attained by the establishment of communication between the two Eider lightships and the Port of Tönning, in

Schleswig, by these means has led to its organisation" elsewhere. This mode of communication is, however, not new, as carrier-pigeons were employed early in this century as a means of communication with the Bell Rock Lighthouse, as mentioned in my late father's "Account" of that work. The pigeons passed between the lighthouse and the shore-a distance of eleven miles in eleven minutes. The employment of these birds, however, was, I suppose, found to be more curious than convenient, for they have long since ceased to be employed. The pigeons were presented to the establishment by the late Sir Samuel Brown, R.N. THOMAS STEVENSON Edinburgh

Globular Lightning

As the curious phenomenon known by the above name seems to be attracting some attention just now, I venture to send you still, owing to their startling character, very fresh in my the following details, which, though of rather ancient date, are

memory.

I think it was in the year 1866, in the beginning of the month of August, that I was walking in the garden when the atmosphere became exceedingly oppressive (there had previously been a very long drought), and thinking by the appearance of the sky, which looked lurid and threatening, that a storm was coming on, I made for the house. As I was going up our front steps some rain-drops fell, which were the largest I ever saw. I had just reached the dining-room and was stand. ing near the window, which looks north, when I saw a large ball of fire, which appeared to me, looking at it as I did from a distance, to be the size of a globe such as is used in schools, descend towards the earth. In descending it struck brought with it a number of slates and part of a stone cross, the church, which is immediately opposite our house, and making a terrific noise. There was a flash of lightning soon after, followed by a moderately loud clap of thunder, but nothing As there were not at that time any houses near to ours I did not hear the occurrence mentioned by any one. The noise, though extremely loud, was not at all like thunder. The illumination of the rooms by the ball of fire was seen by two other persons in the house. CHARLOTTE HARE

more.

St. John's Road, Putney, S.W.

Speaking-Trumpets

THE antiquity of the speaking-trumpet may be proved upon far higher authority than that of the imaginative Athanasius Kircher. It is literally as old as the Pyramids. While exa mining Lepsius's great work upon ancient Egypt for my "History of Music" I noted two examples among the plates of the fourth dynasty of Egypt (see Lepsius's "Denkmäler,' Dyn. 4, Abt. 2, Blätter 27 and 30). The Egyptian speakingtrumpets seem to have been some five feet or more in length, and too wide in diameter to have been blown by the mouth. They are conical, and lack the contraction near the mouth-end which is so observable in their war-trumpets.

Toughened Glass

WM. CHAPPELL

My own experience supports the necessity for caution in using Bastie's toughened glass. Shortly after its introduction I had some graduated measures, and although they were sufficiently tough to bear the shock consequent on falling five or six feet to the ground, yet after a time some short scratches appeared on their surface, and these rapidly spreading till they nearly covered the whole of the glass, when but a slight touch was sufficient to make the measure fly into fragments. One placed on a shelf subject to rather rapid change of temperature, without any handling or apparent cause, broke up suddenly into tiny pieces, behaving, indeed, as if it were a Rupert's bomb. Northampton, October 29 G. C. DRUCE