« AnteriorContinuar »
tained some better tokens of consciousness than the greater or less resemblance of the movements in question to such movements as our conscious selves are in the habit of executing.
Meyer's Exploration of New Guinea
Few persons can have read Dr. Meyer's account of his recent adventurous and very successful journey with more interest than myself; but I confess I was surprised to find that the translator of my book should have misunderstood what I had stated, and so create a difference between us where none exists. He says (speaking of Dorey) that I "have not given a correct impression of the natives of the surrounding hills and mountains, separating them in some way from the inhabitants of the coast, as smaller, uglier, not mop-headed," &c. ; and that he finds on the other hand, that "there is no generic difference at all between the Papooas of the mountain and the Papooas of the coast, except such differences as we find everywhere between the highlanders and coast inhabitants of the same race." Now I say exactly the same thing: "From these (sketches) and the captain's description, it appeared that the people of Arfak were similar to those of Dorey." (" Malay Archipelago," 3rd Ed. p. 505.) Dr. Meyer however, probably refers to what I say of the people of one hill village, close to Dorey: "The inhabitants seemed rather uglier than those at Dorey village. They are, no doubt, the true indigenes of this part of New Guinea, living in the interior, and subsisting by cultivation and hunting. The Dorey-men, on the other hand, are shore dwellers, fishers, and traders in a small way, and have thus the character of a colony who have migrated from another district. These hillmen, or Arfaks, differed much in physical features. They were generally black, but some were brown like Malays. Their hair, though always more or less frizzly, was sometimes short and matted," &c. (p. 499). I can only suppose that the word "differed " in the above passage was taken to mean "differed from the Dorey people," whereas the context shows that it means "differed among themselves," or varied, which would have been a better word. In the preceding page I have stated of the inhabitants of Dorey: "The majority have short woolly hair;" so that there is no difference from them in that respect. In all [ have written about the Papuans I have maintained that the people of New Guinea and of all the immediately surrounding islands are of one race, with very unimportant local differences ; and I do not think my remark, that the people of one village were "rather uglier" than those of another, three miles off, justifies the idea that I supposed there was any "difference," in an ethnological sense, between them. I cannot find that I have said a word about difference of stature.
The great success of both Messrs. D'Albertis and Meyer in penetrating inland in New Guinea will, it is to be hoped, induce other travellers to attempt the exploration of the far larger and less known southern portion. Two Europeans, with a small steam launch and a Malay crew, would, no doubt, be able to penetrate a long way up some of the larger rivers, and establish a station from which exploration of the central mountains might be effected. There is now no portion of the globe so completely unknown as this, or which promises such great results for every branch of Natural History. Alfred R. Wallace
Deep-sea Sounding and Deep-sea Thermometers
With reference to the discussion which has recently been carried on in Nature as to the deep-sea thermometers, I hope that perhaps the following statement may tend to put the matter at rest.
One of Negretti's thermometers was exhibited at the Royal United Service Institution at a lecture, March 11, 1859, by Admiral FitzRoy, who then spoke of them "as thermometers peculiarly constructed, self-registering," &c. The construction of these thermometers had been fully described in the "First number of Meteorological Papers, 1857," and was subsequently given in a "Treatise on Meteorological Instruments," published by Negretti and Zambra in 1864. The peculiarity of these thermometers was mentioned in the Ilydrographic Instructions to Captain Dayman of the Cyclops Sounding Expedition, dated May 29, 1857. These facts are sufficient to show the ample publication of the device in question for protecting the bulbs against pressure.
I know from Dr. Miller himself that he did not know of Negretti's plan. In his paper in the Royal Society Proceedings,
he calls the one which he describes a "simple expedient." I am not aware of any just claim on the part of Mr. Casella to the principle of the invention.
I consider that the practice of instrument makers designating by their names instruments which they have not invented, is most reprehensible. Robert H. Scott
London, Dec. 9
[We have received a letter on this subject also from Mr. Casella, but as there is nothing in it bearing on the real point at issue, we do not print it. The above letter from Mr. Scott renders it clear to us, and it will doubtless be also clear to our readers, that the whole credit of the double bulb belongs to Messrs. Negretti and Zambra. We quite agree also with Mr. Scott's closing remarks. This correspondence must now cease. —ed.]
The Dutch Photographs of the Eclipse of 1871
About a year ago Dr. Schellen kindly sent nie two paper copies of the Java photograph, one of them was stated to be of the size of the original negative and the other was an enlargement of about ten and a half diameters, with a delicately soft outline and much detail in the corona. On comparing this with the Indian photographs I found that though the outline of the corona corresponded depression for depression with the two Indian series, yet there was great difference in the detail of the lower parts. The question therefore arose, Was such difference to be regarded as proof of enormous change in the corona in the course of about an hour, during the passage of the totality shadow from India to Java?
I had carefully compared and catalogued the details visible upon the original negatives of the two Indian series, and had found no structure in the one that could not be traced in the other, but the details of the new Java photograph were quite of a different character, lumpy, and in more definite masses. On mentioning this to Lord Lindsay he informed me that he had other copies of the Java negatives which he had received directly from Prof. Oudemans and which were almost structureless. Mr. Davis undertook a critical comparison of the two Java photographs, and pointed out that in spite of the striking dissimilarity of the paper prints, they were evidently both taken from the same original, for they each showed a faint scratch and three minute photographic flaws in the same relative positions. It was impossible to assert that the one was a good print and the other a very bad one, for in the photograph with the delicate corona the moon's limb was soft and hazy, while with the poor corona the limb was perfectly sharp and definite. We had only one course left, and that was to infer that the softening and details had been produced artificially. Having detected manipulation in the corona, we naturally suspected it in the moon's limb, and thus arose my remark at the meeting of the Astronomical Society, that the sharp edges of the irradiation under the prominences might have been artificially produced by stopping out the moon, or rather by stopping out the hazy irradiation which presents so marked a feature, especially under the prominences in the Indian photographs, as well as in those taken in 1870.
There is still a little mystery which requires clearing up about the hazy irradiation. No trace of it is to be found in the copies of the Shelbyville photograph taken by Mr. Whipple in 1869, nor (as we now learn) in the Java photographs, although the action of the light has been greater in these than in some of the Indian and 1870 negatives, which show it as a very marked feature. We know that under ordinary circumstances hazy irradiation is produced by reflection at the hinder surface of the glass on which the photograph is taken, and that its amount may be greatly reduced by backing the plate, during its exposure, with wet paper, so as to produce a film of water instead of a film of air immediately behind the plate, thus causing nearly all the light to be transmitted instead of reflected at its back surface. Yet the Baikul photographs (and I understand also the Cadiz photograph of 1870) were backed with wet paper, and still show the irradiation very markedly.
The cause of the ellipticity of the dark moon touched upon by Prof. Oudemans seems to me to involve some very interesting questions. It is remarkable that the ellipticity does not occur ia all eclipse photographs. After making allowance for the moon's motion during 40 seconds in the enlargement from the Cadiz negative, I may say that I have not been able to detect any difference between the polar and equatorial diameters in any of the 1876 photographs.
In No. 2 of the glass copies from the Ottumwa photographs, 1869, the moon is also apparently quite circular; but in No. 4, where the bright depths of the chromosphere are just appearing, the polar diameter is distinctly the longest I have been led to conclude that the ellipticity is caused by aii unequal eating over or irradiation at the polar and equatorial portions of the limb, and that in this lies proof that at the sun's equatorial regions the brighter layers of the chromosphere extend to a greater height than near the poles. We know from other sources that the corona generally, and probably also its lower portions, were not so bright in 1870 as in 1869 and 1871 ; hence the eating over between the prominences has been comparatively slight, and no detectable difference has been caused between the polar and equatorial diameters. ■— A. CowrER Ranyard
The British Museum It is strange that such a statement as that advanced by Mr. W. Stanley Jevons in Nature, Nov. 13, has so long remained unchallenged, viz. "that the British Museum exists not so much for the momentary amusement of gaping crowds of country people, who do not understand a single object on which they gaze, as for the promotion of scientific discovery, and the advancement of literary and historical inquiry." No one will dispute the truth of these statements, but substitute the word "instruction" for "momentary amusement," and I very much doubt if his views would meet with public approval. I have always looked upon the British Museum as the National Museum, and pre eminently the Museum of the people, and, as such, the arrangement and labelling of the specimens should be of the most simple and instructive nature : nor is such an object opposed to, but perfectly coincident with, the highest interests of science. No wonder the Museum is filled with *' gaping crowds " when nothing is done to instmct them as to the nature of objects of which Mr. Stanley Jevons himself admits they are ignorant, nor to provide them with a suitable and educational guide-book, without which they are as sheep without a shepherd When the Trustees of this Museum can spare time, they may, perhaps, be able to direct attention to the fuller development of its scientific and educational functions; as regards the former, by the establishment of one exclusively British Department; and, as regards the latter, by carrying out the very obvious suggestions which I have advanced. The view that science, or rather scientific men, should have a monopoly of the benefits to be derived from this Institution is astoundingly selfish and narrowminded. If such are the views of the Trustees, the British Museum had better be closed to the public. S. G. P.
I HAVE recently been visiting some of those spots which, according to Prof. Ramsay and other geologists, are marked by moraines of the ancient glaciers of North Wales, and several of which are supposed to form the retaining walls of lakes or tarns: and a question has arisen in my mind to which neither my own consideration nor any of the few books here at my command has afforded any answer.
A glacier which has retreated from its terminal moraine, is always the source of a stream of water, and this stream always cuts through the terminal moraine, and makes in it a gap often wide, and always reaching down to the level of the original soil. A terminal moraine from which a glacier has retreated is the rim of a saucer with a cleft in it, extending to the bottom of the saucer. It consequently cannot and does not act as a retaining wall, and the water from the glacier does not form a lake, but flows out as a stream. No better illustration of this fact occurs to me than the Rhone glacier, with its long series of terminal moraines, all intersected and cut through to the ground by the infant Rhone. How then can a terminal moraine ever lorm a lake? But if a terminal moraine alone cannot form a lake, a terminal moraine with a stopper put into its; hole might. But how is the stopper to get there? Why should dibris or stones or any other stopper stay in the one place in the whole line where there is no resistance?
Where the basin of the lake is supposed to be constituted by a rock basin and a moraine on its rim, what I have said has, of course, no application to the rock basin, but seems to me to apply to show that the moraine cannot constitute any part of the retaining barrier.
And again, where the retaining barrier is supposed to be constituted by a marine terminal moraine, i.e. by a moraine deposited under the sea, the observations I have made seem not to apply.
My questions apply to ordinary terrestrial terminal moraines. They are so simple and go so to the root of the whole notion that such moraines can form lakes that I presume they have been answered long ago by geologists. Can any of your readers tell me where such answers are given or what they ought to be?
Bryn Gwyn, Penmaenmawr, Oct. 13 Edw. Fry
The Elevation of Mountains and the Internal Condition of the Earth
I Have just read in Nature, vol. ix. p. 62, Captain Hutton's letter to the Rev. Osmond Fisher on the "Elevation of Mountains and Volcanic Theories." I was also indebted some time since to the courtesy of Captain Hutton for a copy of his lecture on the Formation of Mountains, delivered at Wellington, New Zealand, November, 1872. Without entering at present into a discussion upon the particular theory which finds favour with him, I may be permitted to call attention to the fact that Sir William Thomson's views as to the rigidity of the earth have been distinctly called in question in a former number of this journal, which has probably not reached Captain Hutton. I refer to my communication entitled "The Rigidity of the Earth," printed in Nature, vol. vii. p. 288. Captain Hutton expresses his belief that the theory of internal rigidity has probably a weak point somewhere. I venture to think that its weak points are so many as to make it a theory too brittle to form a support to any geological superstructure.
Dublin, November 28. H. IlENNESbY
METEOROLOGIC SECTIONS OF THE
'"THE primary object of meteorology is to record the *■ pressure, the temperature, the moisture, the electricity, and the movements of the atmosphere. It is desirable, however, that observations on these subjects should be combined with the elements of time and distance. At the general meeting of the Scottish Meteorological Society on June 26, 1867,1 proposed the method, since generally adopted, of reducing the intensity of storms to a numerical value by the calculation of barometric-gradients, or in other words by dividing the difference of reading of any two barometers by the distances between the stations where such barometers are placed, thus introducing a nomenclature of universal application, by which the movements of any aerial current, and particularly the wind force of storms, may in every part of the world be reduced to one standard of comparison; and the calculation of thermometric, hygrometric, and electric gradients was subsequently proposed. Since then I suggested to the same society the extension of this system by the establishment of a series of barometers placed at short distances from each other in one or more than one direction in azimuth, so as to give horizontal atmospheric sections for pressure. By means of such lines of section the maximum gradient during storms might, from the nearness of the stations to each other, be ascertained, and thus the phenomena of local storms and other local atmospheric disturbances investigated with some hope of success; and since then a horizontal section extending landwards from the sea-shore has been proposed for temperature and moisture, chiefly with the view of determining the extension inland of the influence of the sea on climate.
It would be important were the system of meteorological sections extended to the vertical as well as the horizontal plane. If a string of stations were placed at short horizontal distances from each other and extending from the bottom to the top of a high hill or mountain, the section thus obtained would show the relative distribution at different times, of pressure, temperature, humidity, &c, in the vertical plane. In Scotland, the existing station of Drumlanrig is 191 feet, and that at Wanlockhead 1,334 feet above the sea, so that the difference in elevation is 1,143 ^eet- The horizontal distance between them is 9 miles, and in all probability the necessary number of intermediate stations could be established. In Hong Kong the town of Victoria is 1,666 feet below that of Blockhouse Victoria Peak, while in Switzerland and other mountainous districts many other suitable places might no doubt be found.
Would it not be possible to secure funds for establishing at least one such atmospheric section on the slope of some steep hill or mountain in connection with a station or two on an adjoining level district of country?
ON THE PHYSIOLOGICAL ACTION OF
AT a meeting of the Royal Society of Edinburgh on the 1st inst., a communication was read from Mr. Dewar and Dr. M'Kendrick on the physiological action of ozone. The authors, in the first place, pointed out that little was known regarding the action of this substance, except its peculiar smell and the irritating effect it had on the mucous membrane of the respiratory tract. Schonbein had shown that a mouse died in five minutes in an atmosphere highly charged with ozone; and it was this distinguished investigator who asserted that there was a relation between the quantity of ozone in the air and the prevalence of epidemic diseases. The action of ozone was therefore a subject to be elucidated; and having occasion to employ ozone in another experimental inquiry, the authors resolved to investigate the matter. The ozone was made by passing a current of dry air or oxygen from a gasometer through a narrow glass tube, bent for convenience like the letter U, about 3 It. in length, and containing a platinum wire 2 ft. in length, which had been inserted into the interior of the tube, and one end of which communicated with the outside through the wall of the tube. Round the whole external surface of this U-shaped tube, a spiral of copper wire was coiled, and the induction current from a coil giving half-inch sparks was passed between the external copper to the internal platinum wire, so as to have the platinum wire as the negative pole in the interior of the tube. After the stream of gas was ozonised by the transmission of the induction current, it was washed by passing through a bulb-tube containing caustic potash, when air was employed, or water when pure oxygen was used, in order to eliminate any traces of nitrous and nitric acids that might have been formed. By means of the gasometer, the volume of gas passing through the tube could be ascertained.
The action of ozone was determined (1) on the living animal enclosed in an atmosphere of ozonised air or of ozonised oxygen ; and (2) on many of the individual living tissues of the body. Numerous experiments were made on frogs, birds, mice, white rats, rabbits, and on the authors themselves. Two experiments may be given here as illustrating the action of ozone on (1) a cold, and on (2) a warm-blooded animal.
1. On a Frog.—A larue, healthy male frog was introduced into the air chamber, through which a current of air was passing sufficient to fill a litre jar in three minutes. At the end of two minutes, the respirations were ninetysix per minute. The induction machine was then set to work so as to ozonise the air. In half a minute, the eyeballs were retracted, so as to appear deeply sunk in the orbits, and the eyelids were closed ; the respirations were now eight per minute. At the end of six minutes, the animal was motionless, and there were no respiratory movements. Pure air was then introduced. In half a minute, there was a slight respiratory movement, and in eight minutes there were eighty-five respirations per minute. At the end of other twelve minutes, ozone was again turned on, with the same result. A frog will survive in a dormant condition in an atmosphere of ozonised air for several hours. In one case, the animal died. The heart was found still pulsating. It was full of dark blood. The lungs were slightly congested. The blood was venous throughout the whole body. In ozonised oxygen the effects were, on the whole, the same as in ozonised
air, with this difference, that in ozonised oxygen the respiratory movements were not affected so quickly, and were never completely arrested.
2. On a White Mouse—A full grown and apparently healthy white mouse was introduced into a vessel through which a stream of air was passing at the rate of eight cubic inches per minute. Five minutes thereafter, the animal was evidently at ease, and the respirations were over 100 per minute. The air was then ozonised. One minute after, the respirations were slower, but the number could not be ascertained owing to the animal moving uneasily about. In four minutes from the time of the introduction of the ozone, the respirations were thirty-two in a minute. The mouse now rested quietly, occasionally yawned, and, when touched by a wire, moved,—but always so as to remove its nose from the stream of ozonised air. At the end of fifteen minutes, the animal had slight convulsive attacks, which increased in severity until it died—nineteen minutes after the introduction of the ozone. The post-mortem appearances were great venous congestion in all parts of the body. The heart pulsated for several minutes after systemic death. In ozonised oxygen, death was delayed for a much longer period. Instead of dying at the end of fifteen or twenty minutes, as happened to mice in ozonised air, they lived for forty or sixty minutes. It is noteworthy that even after death in ozonised oxygen, the blood was found to be in a venous condition.
On breathing an atmosphere of ozonised air themselves, the authors experienced the following effects :—a suffocating feeling in the chest; a tendency to breathe slowly; irritation of the fauces and glottis j a tingling of the skin of the face and conjunctivae. The pulse became feebler. The inhalation was continued for eight minutes, when they were obliged to desist; and the experiment was followed by violent irritating cough and sneezing, and for five or six hours thereafter by a sensation of rawness in the throat and air-passages.
The general result of the inquiry may be briefly stated as follows :—
1. The inhalation of an atmosphere highly charged with ozone diminishes the number of respirations per minute.
2. The cardiac pulsations are reduced in strength and this organ is found beating feebly after systemic death.
3. The blood is found after death to be in a venous condition, both in those cases of death in an atmosphere of ozonised air and of ozonised oxygen.
4. The inhalation of an ozonised atmosphere is followed by a lowering of the temperature of the body to the extent of at least 30 to 5° C.
5. The inhalation of ozone does not exercise any appreciable action on the capillary circulation, as seen in, the web of the frog's foot under the microscope (200 diameters).
6. In the bodies of frogs killed in an ozonised atmosphere, the reflex activity of the spinal cord is not appreciably affected.
7. By means of a myographion, the work done (in gramme-millimetres) by the gastronemius muscles of frogs subject to the action of ozone was noted. The muscles were stimulated by a single opening or closing induction shock produced by Du-Bois Reymond's apparatus and a Daniell's cell. The result was that the contractility and work-power of the muscle were found to be unaffected.
8. Ozone has an action on the coloured and colourless corpuscles of human blood and of frog's blood resembling that produced by a weak acid; and in the case of the coloured corpuscles of the frog like that of a stream of carbonic acid. The corpuscles of animals killed in an ozonised atmosphere are normal in appearance.
9. Ciliary action is not affected by a stream of ozonised air or oxygen, provided there is a considerable amount of fluid covering the cilia; but if the layer of fluid be very thin, the cilia are readily destroyed.
In conclusion, the authors stated that it would be premature, at this stage of the inquiry (which opened up many points of interest in the physiology of respiration), to generalise between physiological action and the physical and chemical properties of ozone; but they pointed out the fact that the density of ozone (03 = 24) is slightly greater than than that of carbonic acid (C02= 22); and that although the chemical activity of the substance is much increased, yet, when inhaled into the lungs, it must retard greatly the rate of diffusion of carbonic acid from the blood, which accounts (from the accumulation of COj) for the venous character of that fluid after death. From this point of view, destruction of life by ozone (with the exception of its irritant action) resembles that caused by an atmosphere surcharged with carbonic acid. This has been found to be the case more especially as regards the diminished number of respirations per minute, and the appearance of the blood after death. If, however, the analogy were perfect, the inhalation of an atmosphere of ozonised oxygen would not have produced death, because it is now well known, as shown by Regnault and Reiset,* that animals can live in an atmosphere containing a large per-centage of carbonic acid, provided there is an excess of oxygen present. The amount of oxygen in these experiments converted into ozone certainly never exceeded ten per cent. But the authors have observed that an animal lives only a somewhat longer time in ozonised oxygen than in ozonised air; and they are thus induced to regard ozone as having some specific action on the blood that their future experiments may elucidate. They are now prosecuting a series of researches (ti) on the action of smaller percentages of ozone; (?>) on the action of ozone on noxious gases and effluvia; and (c) on any therapeutical or hygienic influences it may have on the origin and treatment of zymotic diseases.
taken against these three sorts of danger. The degree of polish is sufficiently perfect, being obtained without hammering, by pushing the tube along a mandril before it becomes completely cooled. The joints represented in Fig. 2 (p. 66), give an almost mathematical continuity to the interior surface, and they are rendered air-tight by means of India-rubber fittings. In this direction, then, there is little risk of damage and the consequent stoppage of the trains. In fact, since 1866 there has not been a single accident caused by any defect in the tubes, and the experiment is made upon a length of twenty kilometres of pipes so constructed that joints occur every five metres.
The derangements arising from the machinery for compressing the air are not of a special character, and need not be particularised here. There remain the boxes. Numerous types were tried before the system of the two cases in tin and leather, which can be hermetically closed and are easily opened; from its simplicity this method has been adopted. Nevertheless it does sometimes happen that the boxes open during the journey; how this is caused is not easy to explain in each particular case. Sometimes the collarette of the piston is in a bad condition, and the air divides the train; the cases are separated, and the despatches are scattered in the tube. At other times wrinkles are formed in the envelope of leather, the effect of which is to wedge the train so firmly that it is impossible to make it move. Another form of derangement is when the piston breaks and the pieces are lodged between the boxes and the tube. It is scarcely possible to exhaust the series of accidents of this nature; the mean number of derangements in the working of the system during the year is eight, and it is rare to find the same cause occurring twice. When accidents do occur, it is necessary to make all haste to relieve the train.
Often alternate manoeuvres with compressed and ratified air removes the obstruction ; at Berlin, for the same purpose, M. Siemens employs water with which he forcibly inundates the tube. The great thing is to extricate the train without having to take the line to pieces. When such means fail it is necessary to have recourse to the operation of excavation ; and the necessity will be evident of a preliminary and sufficiently exact determination of the place of derangement. The first means is indicated by the method on which the system is worked. There is at hand a reservoir of compressed air of a certain pressure; if this air is pnrtly distributed in the section of the tube comprised between the reservoir and the obstacle, the new pressure is in a known ratio to the original pressure. In a word, Mariotte's law, which regulates the ratios of the pressures and volumes of the same mass of gas in two different circumstances, furnishes the means of finding one of the elements, volume, when we know the three others, two pressures and one volume.
M. Siemens prefers to measure the quantity of water which it is necessary to distribute in order to flood the line as far as the obstacle; the accuracy ought to be very great, but it must be acknowledged that the process, in spite of its apparent simplicity, has a somewhat primitive aspect. It is not difficult to understand how this great mass of water is introduced, but it is very difficult to conceive that it can easily remove the obstacle.
We may speak, finally, of an indirect means which is illustrated in Fig. 4. The reader knows that when a concussion is produced at the end of a tube filled with air, this concussion is propagated in the air of the tube at a speed of 330 metres per second. When the concussion encounters an obstacle, it is reflected and returns to the point of its origin at the same rate of 330 metres per second. If then the time is noted which elapses between the departure and the return, the period thus obtainedcor responds to the passage of the concussion along a distance equal to double the distance of the obstacle; from an observation of the time, the distance can be easily calculat'J For example :—The interval of time between the departure and return of the wave produced by the concussion is \ of a second; the double journey is represented by
330 m. _ a^ ^e distance of the obstacle is
3 2 = 55 metres.
The times of the departure and of the return of the wave are graphically registered on a chronograph, by the interruption of an electric circuit obtained by the motion of a-membrane of caoutchouc placed at the extremity of the tube.
It is known that an electric current magnetises- a horseshoe magnet The magnetisation of the magnet communicates to a palette placed above the poles, an attraction which ceases as soon as the current is broken. Without entering into further explanation of this wellknown arrangement, which is the basis of nearly all telegraphic apparatus, it will be granted that with conveniently placed conductors it will be possible
to make the armature of the magnet move like the elastic membrane; in other words, if the membrane is raised 2, 3, 4 times in a second, the armature will be connected 2, 3, 4 times, and the durations as well as the intervals of the contacts will be identical in the two apparatus.
Let us return to the chronograph. The time is marked by it, and is recorded by means of electromagnets. The oscillations of a seconds pendulum are repeated electrically and registered on a line, No. 2 in Fig. 4, which is described by a point fixed to the electro-magnet, upon a smoke-blackened cylinder, to which is given a movement of continuous rotation. The electro-magnet whose point describes line No. 2, is moveable on a carriage that advances along the cylinder in the same time as the latter takes tc- turn. The carriage bears two other electro-magnets: one corresponds to a sub-divisor of the time which gives fractions less than a second. It is this which
traces line No. 1, representing by its tracings sub-divisions equal to g^rd of a second; this division into fractions corresponds to the oscillations of the palette of an electric tremblcur, a contrivance in which the interruptions and re-establishment of the current take place at the rate of 33 per second in the model here represented.
The third electro-magnet, in connection with the membrane of caoutchouc, corresponds to the movement of the wave in the tube ; it furnishes line No. 3 in the figure. It may be remarked that the same wave undergoes many successive reflexions.
It will be easily seen from the diagram how the result sought can be obtained from the experiment. Suppose the obstacle to be placed at 62 metres ; the interval between two successive marks of the membrane is about 12 sub-divisions. A comparison of lines 1 and 2 shows that there are 33 sub-divisions in one second ; the indications of line 3 then are equal to Jij of a second. The
double distance represents Jp, X 330 m, and the simple length given by the experiment is thus about \ X \\ X 330 = 60 metres, the result sought to within 2 metres.
Fig. 4 shows the method adopted for producing the wave. On the left T is the tube in which a small pistol V is placed to produce the detonation which gives rise to the wave. On the table in the centre of the figure is the chronograph ; M is the clock-work which turns the registering cylinder, on the surface of which are traced the lines 1, 2, 3; S is the carriage bearing the three electromagnets, each of which traces its line. The electromagnet on the right, line I, is the tremblcur, in connection with the pile P P". The middle electro-magnet, line 2, is connected with the seconds pendulum R. Finally, the electro-magnet on the left, line 3, communicates electrically with the caoutchouc membrane that surmounts the tube T, and exactly fits the opening, on which it is stretched like a drum-skin.