240 



NATURE 



\yan. 20, 1876 



accurately arranged side by side. It is advisable always to 

 observe the image of the electric arc when comparing the spec- 

 tra of metals with that of the sun, rather than direct light. It is 

 also found very advantageous to place the poles of the lamp 

 at right angles to the slit, as by this means the long and short 

 lines in the spectra are more sharply defined than when ob- 

 served in the ordinary manner. In the photograph com- 

 paring the spectra of aluminium and calcium it is noticeable that 

 certain lines are common to the two, but those which are thick in 

 the aluminium spectrum are thin in that of calcium, and vice 

 versd. This depends on the quantities of impurity present. It 

 has thus been shown that there are no proper coincident lines in 

 the spectra of any two simple substances, and that there is no 

 substance spectroscopically pure. The relation between the 

 lengths of the lines and the amounts of metals employed to pro- 

 duce the spectrum convinced Mr. Lockyer that it would be pos- 

 sible to employ the spectroscope for quantitative analysis. The 

 earlier experiments in this direction were then referred to, as well 

 as those on which Mr. Lockyer has recently been engaged in con- 

 junction with Mr. W. Chandler Roberts, of the Royal Mint, with 

 a view to ascertain how far it is possible to detect small differ- 

 ences of composition in gold-copper alloys such as that used for 

 the coinage. The method employed was then described. It con- 

 sists in measuring, by means of a micrometer in the eye-piece of 

 a four-prism spectroscope, the relative lengths of certain gold and 

 copper lines when the image of an induction coil spark passing 

 from the alloy under examination is focussed on the slit. Al- 

 though the results obtained have not been uniformly comparable, 

 and therefore reliable, it is nevertheless certain that a difference of 

 composition as minute as the TTrrxnrth part is recognisable by this 

 means. Another method of spectroscopic research which Mr. 

 Lockyer next described was the study of the absorption spectra of 

 metals when they are not subjected to so violent an action as that 

 of the electric arc. Observations of this nature have been made 

 at low temperatures by Roscoe and Schuster, and by Mr. Lockyer, 

 and at the highest temperatures produced by the oxyhydrogen 

 blow-ripe by the latter in conjunction with Mr. Roberts. These 

 experiments, which have been fully described in the Proceedings 

 of the Royal Society, show that the absorption spectra of metals 

 may be divided into five classes, which, for any particular metals, 

 depend on the amount of heat applied. They suggest that 

 in passing from the liquid to the most perfect gaseous state, 

 vapours are compost d of molecules of different orders of com- 

 plexity ; and that this complexity is diminished by the dis- 

 sociating action of heat, each molecular simplification being 

 marked by a distinctive spectrum. — The President inquired 

 whether the iridium line to which Mr. Lockyer had referred, and 

 by means of which the metal was originally discovered, ^was 

 absolutely identical with a hydrogen line. — Prof. McLeod 

 asked if Mr. Lockyer had found that the incandescence of the 

 air made any difference in the character of the spectra, and drew 

 attention to the advantage of a small lens placed in front of the 

 slit. — Mr. Woodward inquired whether any mechanical means 

 were adopted for ensuring that the lamp gave a constant 

 light while in the horizontal position. — Dr. Guthrie referred 

 to the spectrum observed when light traverses the vapours 

 resulting from the action of copper on nitric acid. He wished 

 to know whether the number of bands observed stands in 

 any relation to the number of possible oxides of nitrogen 

 at a given temperature ; or must one oxide of nitrogen be con- 

 sidered as being capable at that temperature of giving bright 

 and dark bands according to the way in which the light acts on 

 it? — Mr. Lockyer, in reply to the president's question, said that, 

 so far, no difference has been observed between the refrangibility 

 of the hydrogen line and that of iridium. He is anxious to ascer- 

 tain whether any occluded hydrogen exists in the metal. Little 

 or nothing is known as to the subject referred to in Dr. Guthrie's 

 question. The use of the electric lamp eliminates] all difliculty 

 with reference to air lines, as its "atom- shaking" power is not 

 sufficient to break up to the line stage the molecules of nitrogen 

 and oxygen. It was found necessary to make the adjustments re- 

 ferred to by Mr. Woodward entirely by hand. 



Victoria (Philosophical) Institute, Jan. 17. — ^On the Sci- 

 entific Conclusions and Theological Inferences, in a recent work 

 entitled "The Unseen Universe," was read by the Rev. Pre- 

 bendary Irons, D.D., the Bampton Lecturer for 1870. 



Paris 

 Academy of Sciences, Jan. 10. — Vice- Admiral Paris in the 

 chair. — The following papers were read : — Experimental critique 



on the formation of saccharine matter in animals, by M. CJ. 

 Bernard ; an apetyn of his researches on the subject. — Researches 

 on aldehyde, by M. Berthelot. He measures the heat liberated 

 in transformation of aldehyde into acetic acid, and into oxalic 

 acid, the heat of vaporisation, &c.- -Union of carburets of 

 hydrogen with hydracids and halogenic substances, by M. Ber- 

 thelot. — Micrometric measurements taken during the transit of 

 Venus, by M. Mouchez. —On the causes of failure in searching 

 for minimal quantities of iodine, by M. Chatin.— New considera- 

 tions on the regulation of slide valves, by M. Ledieu.— M. 

 Mouchez presented some new maps of the ^coast of Africa. — 

 Report on the project of a physical observatory on the top of 

 the Pic du Midi de Bigorre, submitted to the Academy by 

 General de Nansouty, in name of the Societe Ramond. This 

 peak (in the Pyrenees) is 2,877 metres in height, and only 527 

 short of the highest. It is somewhat isolated, and receives the 

 direct shock of the great Atlantic air-currents ; and it is easily 

 accessible. A small hotel on the Col de Sencours (511 m. lower) 

 has been provisionally used for observations since 1873, but amid 

 great difficulty, from avalanches, &c. — Report on a memoir en- 

 titled " Probleme inverse des brachistochrones," by M. Hatonde 

 la Goupilliere. — Influence of tempering on magnetisation, by M. 

 Gaugain. The bars hardened most are those which take the 

 greatest magnetism, when one uses the most powerful means of 

 magnetisation ; but annealed bars are magnetised most power- 

 fully where less energetic means are employed. — On the recent 

 falling in on Bourbon Island, by M. Velain. The disaster was 

 due to disaggregation of certain volcanic rocks under atmospheric 

 agencies. — On a subterranean commotion in the centre of the 

 isle of Reunion ; disappearance of a hamlet of sixty-two persons, 

 by M. Vinson. — On a pocket telemeter with double reflection, 

 by M. Gauraet. — On the winter egg of Phylloxera, byM. Boiteau. 

 — M. Carvalho presented a model of an ozonogenic apparatus, for 

 rendering apartments wholesome in hot and unhealthy climates. 

 It is a kind of condenser of the electric effluve. M. Thenard gave 

 a warning on the poisonous action of ozone. — Generalisation of the 

 theory of an osculating radius of a surface, by M. Lipschitz. — Note 

 on a particular class of left decagons, inscriptible by an ellipsoid, 

 by M. Serret. — Note on the application of recurrent series to 

 investigation of the law of distribution of primary numbers, by 

 M. Lucas. — On the spectrum of gallium, by M. Lecoq de Bois- 

 baudran. With chloride of gallium he gets two narrow lines, 

 a 41 70 and /3 403 'i. — On the decrease of sugar in beets during 

 the second period of their vegetation, by M. Cosenwinder. — On 

 the installation of the Meteorological Observatory of the Puy de 

 Dome, by M. AUuard. Observations (every three hours) were 

 commenced on Dec. 20, 1875. A station on the plain, at Cler- 

 mont, 9 kil. distant, and i,ioom. under the summit, is supplied 

 with the same instruments, and the tv/o stations are connected 

 telegraphically. — On the periodic movements of leaves in Abies 

 nordmanniana, by M. Chatin. 



CONTENTS Page 



The "Encvclop.'edia Britannica." By Prof. A. Garrod ... 221 



Fossil Butterflihs 222 



Burchett's " Practical Plane Geometry" 224 



Our Book Shelf :— 



Meteorology in Havana 224 



Letters to the Editor :— 



Blowpipe -Analysis.— Major W. A. Ross 22^ 



The D-line Sptctrum.— Major W. A. Ross 224 



The Difference of Thermal Energy Transmitted to the Earth by 

 Radiation from different parts of the Solar Surface.— Capt. J. 



Ericcson. {IVith Illustrations) 224 



The Glow-worm in Scotland.— David Robertson 225 



Our Astronomical Colu.mn : — 



Star with Suspected Large Proper Motion 226 



Atlas " 27/ Pleiadum 226 



Variable Stars - 227 



Recently-discovered Minor Planets 227 



The New Museum OF the Geological SociETV 227 



Condensed Air Tramways 228 



The Great Telescope of the Paris Observatory. ( H^itft Illust- 

 ration) ^■^^ 



The Loan Exhibition of Scientific Apparatus at South 



Kensington 231 



Beats in Music, I L By W. Pole, F.R.S., Mus. Doc. O.von. . . 232 



Notes ^34 



Scientific Serials ^37 



Societies and Acapxmiks . • • • t • • 237 



