May 4, 1876] 



NA TURE 



19 



I experiments which will be exhibited on a future occasion, the 

 author concludes that the cause of the phenomena is obvious, 

 ard that the hypothesis of a new force is unnecessary. — Prof. 

 McLeod referred to a paper on the same subject which appeared 

 ii; the Chemical News of April 28, by Messrs. Houston and 

 Thomson.— Mr. David Ross, B.A., inquired the tension of the 

 Lcyden jar arrangement used in the experiments, but Mr. 

 liiompson pointed out that it would be very difficult of deter- 

 mination on account of the rapid change of the spark from 

 positive to negative. 



Manchester 



Literary and Philosophical Society, Jan. 25.— Mr. E. W. 

 Binney, F. R. S. , vice-president, in the chair. — On stannic arsenate, 

 by Mr. William Carleton Williams, F.C.S., Demonstrator in the 

 Chemical Laboratory of the Owens College. 



Feb. 8. — Ordinary meeting. — Mr. Edward Schunck, F.R.S., 

 president, in the chair,— Prof. C. Schorlemmer, F.R.S., read a 

 communication from Prof. Sadtler, of the University of Pennsyl- 

 vania, on some of the natural gases from the gas wells in Butler 

 County, Pennsylvania, in the midst of the oil region. — Notice of 

 a recent discovery of a prehistoric burial place near Colombier, 

 in Switzerland, by Mr. William E. A. Axon, M.R.S.L. — Mr. 

 Brockbank, F.G.S., exhibited a large collection of granites from 

 the Ravenglass district, and from Criffel, which he had got to- 

 gether with a view to proving the origin of the large granite 

 boulders recently found in the Glacial clay or till of this district. 

 — On the formation of azuriteirom malachite, by Mr. Charles A. 

 Burghardt, Ph.D.— On a direct-vision spectroscope of great dis- 

 persive power, by Mr. Arthur Schuster. This instrument is 

 made by Mr. A. Hilger, of London. The following are its chief 

 advantages : — I. The compound prism has a very great dispersive 

 power. The nickel line between the two sodium hnes is easily 

 seen in the solar spectrum. 2. The cross wire is replaced by a 

 very fine slit which can be illuminated from above to any degree 

 of intensity. 3. The slit is moveable by means of a very fine 

 micrometer screw ; the position of the slit can be read off" to 

 within o-oooi inch. The measurement is made by bringing the 

 line to be measured against the bright slit which comes down 



Ifrom the top to the middle of the field. The position of the 

 lines can be easily measured to within the fifth part of the dis- 

 tance between the sodium lines. — On a new absorptiometer, by 

 Mr. Arthur Schuster. In some recent researches Prof. Vogel 

 fovmd that the relative intensity of the red and blue part of the 

 solar spectrum was subject to great changes. While working 

 with the spectroscope at considerable heights on the southern 

 slope of the Western Himalayas, I was struck by the same fact 

 The instrument which I have now the honour to exhibit before 

 the Society is constructed in order to measure the relative inten- 

 sity of the red and blue hght in the solar or any other spectrum, 

 by comparing the intensity of each ray with that given out by a 

 standaid lamp. The photometric principle involved in the mea- 

 surement is that first used by Prof. Zollner. The intensity of a 

 certain part of the spectrum is brought to the same intensity as 

 that of the standard light by a system of Nicoi's prisms. Prof. 

 Zollner only compared the whole intensity ol two sources of light 

 , and did not investigate the relative intensity of the different 

 colours. Mr. D. Glau constructed another apparatus by which 

 he could measure the relative intensity of different colours, but 

 his instrument was constructed ior an entirely different object, 

 and is not suitable for the purpose for which the present instru- 

 ment is made. The instrument, which I have called absorptio- 

 meter, because it is intended chiefly for the determination of the 

 absorption of light taking place in our atmosphere, consists of a 

 X table similar to that of a goniometer table, but being able to turn 



1 round on a horizontal axis so as to give it any inclination 

 to a horizontal surface. The telescope of the goniometer 

 is replaced by a direct-vision spectroscope. Opposite the spec- 

 troscope a tube is fixed to the table containing two Nicoi's 

 prisms. One of the prisms is fixed, the other can be turned, 

 and its azimuth read off on a graduated circle. The standard 

 light is placed behind its tube. The intensity of the hght falling 



unto the slit of the spectroscope is — sin o, where a is the angle 



between two of the principal planes of the two Nicol prisms, 

 and A the intensity of the light which would fall into the sht of 

 the spectroscope if the Nicoi's were removed. A plane parallel 

 piece of glass, acting as a mirror, is fixed unto the small table, 

 the centre of which coincides with the centre of the large gonio- 

 meter table. The parallel sides can be adjusted by means of 

 three screws until they are vertical. This mirror reaches to such 



a height that the horizontal plane laid through the top of the 

 plate would bisect the tube containing the two Nicols. The light 

 which is to be examined falls through a tube containing one 

 Nicol, and is reflected by means of the plane parallel mirror into 

 the lower half of the spectroscope. If the ray of light is reflected 

 at the angle of polarisation the intensity of this hght can be 

 reduced to nothing by means of the rotation of the Nicol. On 

 placing the standard light in front of the tube containing the two 

 Nicols and allowing the light which is to be exammed to be 

 reflected into the spectroscope on the mirror through the tube 

 containing one Nicol, the mirror being placed at the angle of 

 polarisation, we observe in the spectroscope the two spectra one 

 above the other, and by turning the Nicols we can reduce the 

 intensity of the brighter light to that of the weaker for any 

 colour we like. The positions of the Nicols will enable us to 

 find the relative intensity of the two lights for the differoit 

 colours. 



Paris. 



Academy of Sciences, April 17. — Vice- Admiral Paris in 

 the chair. — The following papers were read : — New researches 

 on pyrogenous carburets and on the composition of coal gas, by 

 M. Berthelot. Benzine is the most abundant carburet, after 

 formene, in Parisian gas ; it is about 3 per cent, of the volume, 

 and is, par excellence, the illuminating carburet. — On the direction 

 of trees thrown down by tornados or trombes, by M. Faye. 

 An observer in the central trajectory of the meteor (which turns 

 from right to left in our hemisphere), and looking in the direction 

 of the motion of translation, will distinguish, in the ravaged 

 band, a right and a left region, and in the trombe an anterior 

 and a posterior half. Then, in the right region, the trombe can 

 throw down well rooted trees by the mere attack of its anterior 

 part, but in the left region it overthrows them by the successive 

 actions of its anterior and its posterior parts. The effects of a 

 cyclone or tornado at sea are analogous. — On the carpellary 

 theory according to the Amaryllideae (second part, Cliina nobilis), 

 by M. Trecul. — Memoir on the existence, the optic and crystallo- 

 graphic properties, and the chemical composition of microcline, 

 a new species of trichnic felspar vidth base of potassium, by M. 

 Des Cloizeaux, — Observations made at the Observatory of 

 Toulouse with the large Foucault telescope, by M. Tisserand. 

 It has been in use since the beginning of February ; the observa- 

 tions described are on the nebula of Orion and on the satelUtes 

 of Uranus and Jupiter. — Researches on M. Wirmerl's compen- 

 sating balance for chronometers, by M. Caspari. — Conclusions 

 from actinometric measurements made on the summit of Mont 

 Blanc, by M. Violle. He obtains, for the effective temperature 

 of the sun, the value of about 1,500° C, which gives, for the 

 probable mean temperature of the surface, a number between 

 2,000° and 3,000°. — New researches on '.he effects of powder in 

 arms, by M. Sarrau. He constructs new formulae for the 

 velocities and pressures, and deduces the laws according to 

 which these quantities depend not only on the conditions of 

 charging, but on the nature of the powder and the form of the 

 grains. — On the ozone of atmospheric air, by M. Marie-Davy. 

 Comparison by means of ozonoscopic papers are very uncertain. 

 The author sought to associate the rapidity of action of iodide of 

 potassium with the stability of arsenical action ; mixing pure iodide 

 with equally neutral and pure arsenite of potash. From observa- 

 tions at Montsouris, March 15 to 31, it appears that the average 

 proportion of ozone in the air by night was 0*76 mg. (per 100 

 cubic metres), and thus considerably less than that by day, viz., 

 1*13 mg. The volume of air operated on each time varied from 

 2 to 3 cubic metres. — The elephants of Mont Dol ; attempt at 

 organogeny of the system of molar teeth of the mammoth (third 

 communication), by M. Sirodot. — Note on the discovery of a 

 human station, of the epoch of polished stone, near Belfott, by 

 M. Ch. Grad. — Elements of the new planet Una, by M. Peters. 

 — Elements and ephemerides of the planet (148) Gallia, by M. 

 Bossert. — Generalisation of the theorem of Lame on the impossi- 

 bility of the equation x' -ir y' ■\- z? = o, by M. Genocchi. — Note 

 on the foci of a plane curve, by MM. Gibert and Niewenglowski. 

 ' — Researches on the elasticity of the air under small pressures, 

 i by M. Amagat. Under small pressure air still follows Mariottc's 

 I law. The opposite has been asserted by MM. Mtndeleeff and 

 Kirpitschoft, and that '.he departure from the law is in the same 

 ! direction as that of hydrogen. — On the nerve terminations in the 

 electric apparatus of the torpedo, by M. Rouget. — Undulations 

 of the chalk in the north of France. Part III. Age of the undu- 

 i lations ; by M. Hebert.— Daubreite (oxychloiiae ol bismuth), a 

 new mineral species, by M. Domeyko. — On chronic caseous 



