36o 



NATURE 



\Atig. 29, 1872 



spectra is the reversal of the absorption bands of tlie vapour of 

 these bodies ; while tlie others are spectra of lines. In the 

 coloured vapours, the molecular constitution must be much more 

 complex than in gases, and it is, therefore, not astonishing tliat 

 sucli a coloured vapour should exert an absorptive influence re- 

 sembling more that of a liquid than of a gaseous body. It would, 

 therefore, show absorption bands, and if luminous, it will not 

 show a spectrum of lines, but a spectrum of bands. At a higher 

 temperature, however, when the vapour becomes a gas. the spec- 

 trum may change to one of lines. As a fact bearing upon the 

 subject, I may mention the discovery made by Kundt, that nitro- 

 gen telroxide gives the same absorption bands, whether in the 

 form of a liquid, or in that of a vapour. 



Preliminary Report of the Committee on inverse Wave-Lengths. 



The reference of spectral lines to a standard scale of wave- 

 numbers, instead of to a scale of wave-lengths in air of a given 

 pressure and temperature, or to any of the other scales in use, 

 has very marked advantages. The scale of wave-numbers fur- 

 nishes to the theoretical inquirer the ratios lictween wave-lengths, 

 — which arc what he chiefly wants— in the simplest and most 

 conspicuous form ; since a series of rays, of which the wave- 

 lengths are in geometrical proportion, will be represented by 

 equidistant lines upon the map. Accordingly the committee 

 decided on reducing to wave-numbers all the wave-lengths, 

 whether of solar lines or of tlie rays of incandescent vapours, 

 which have been determined with sufficient precision. Mr. C. 

 E. Barton has offered his services gratuitously for making the 

 necessary reductions, and has made considerable progress with 

 the solar spectrum. A specimen of the catalogue of solar lines 

 was appended to this report, containing the lines from E to /'. 

 It is intended that this catalogue shall contain the most useful in- 

 formation available — namely, references to the position of each 

 line on Kirchhoff's or Angstrom's maps, details of the processes 

 by which the standard wave-numbers have been deduced, and 

 indications of the intensity, width, and origin of each ray when-_ 

 ever these have been determined. The rays will, moreover, be 

 bracketed into the groups that strike the eye in looking at the 

 spectrum, and a number will be assigned to each group which 

 will sufficiently indicate its position on the standard scale. It is 

 estimated that the two catalogues— namely, the catalogue of the 

 principal Ihies of the solar spectrum, and the catalogue of rays 

 of incandescent vapours, will cost about 60/. The committee 

 think that they could render the second catalogue more perfect 

 if they were in a position to employ a competent person to revise 

 and extend the determination of the rays of incandescent vapours, 

 and they therefore suggest that this revision be made a part of 

 their functions, and that an addition of 50/. be made to the grant 

 for this purpose. This would increase tlie sum to be granted 

 this year to 150/. The committee accordingly recommend that 

 they be reappointed, and that this sum be placed at their dis- 

 posal, in addition to the balance at present in their hands. 



.SECTION B— Chemical Sciexcf. 



Thursday, Aug. 15. — At tlie close of the Tresident's address, 

 Dr. Wright read the Report of the Committee for Investigating 

 the Chemieal Constitntion and Optical Properties of the Essen- 

 tial Oils used for Perfumes, which was followed by a short dis- 

 cussion, in which Mr. Ilanliury pointed out the necessity of 

 paying particular attention to the characters of the samples of 

 ilie various oils taken for experiment, and he instanced several 

 essential oils classed under the same name but of widely different 

 oiigin and possessing wholly different properties. He was 

 under the impression that sufficient care had not been taken in 

 the selection of the samples with which experiments had hitherto 

 been worked. 



I'rof. Mallett, of Virginia, U.S., exhibited some specimens of 

 fused metallic arsenic which he had prepared by fusing the metal 

 under great pressure. The fact tliat arsenic can thus be fused 

 has already been determined by Landolt. 



Prof. Mallett also gave an interesting resume' of his experi- 

 ments on the nature of the gases occluded by meteoric iron. 

 The method employed by him was essentially that of Graham, the 

 meteorite being heated in a vacuum and the evolved gases removed 

 by tlie Sprengel pump. The nature of the iron remaining was 

 carefully examined, and it appeared that the heat modified the 

 metal in a remarkable manner, principally as regards its capability 

 ol being forged. The original meteorite could be readily forged 

 and beaten out into a tolerably perfect blade for a paper-knife, 



but on strongly heating the iron so as to drive ofl' the occluded 

 gases (principally hydrogen, carbonic acid, and carbonic oxide) 

 it became cold-short, and could not be forged even with extreme 

 care. The cause of the remarkable alteration in the tenacity of 

 the metal gave rise to some discussion, from which it generally 

 appeared that it was due to an alteration of the schreiberite 

 in the meteorite. 



Mr. W. I,. Carpenter gave a short account of the methods 

 employed in the recent dredging operations for collecting deep 

 sea water. In the discussion which followed Prof. Crum-Lrovvn 

 desciibed the method to be followed in the forthcoming expedi- 

 tion. The appaiatus had been proved to work exceedingly 

 well in shallow water, but it remained to be seen how far it 

 could be used in the open ocean and under great pressure. 



Prof. Thorpe exhibited a modification of the filter-pump re- 

 cently described by Mendelejeffi It acts upon the principle of 

 the hydraulic ram, and by means of a fall of water of less than a 

 yard a vacuum of nearly 700' can be readily ebtained. The 

 modification consisted in the nalure of the valve employed and 

 in the method of determining the degree of exhaustion. The 

 instrument has the advantage of portability and readiness of 

 construction over the older form of I!uns:ed (which requires a 

 fall of water upwards of 30 ft,), and is likely to come into general 

 use. 



Dr. Russell read a paper prepared by Dr. Moffalt on the tube 

 ozonometer, which elicited some discussion as to the value of 

 ozonometric observations conducted by means of iodide of potas- 

 sium papers. The use of such papers was generally condemned 

 by the members of the Section ; but the meeting arrived at no 

 definite conclusion respecting any other way in which the libera- 

 tion of iodine may be utilised as a measure of ozone. 



Mr. C. J. Woodward exhibited and described a very simple 

 and cheap modification of Ilofiiiann's Apparatus for the Elec- 

 trolysis of Water. 



Friday, Aug. l5. — Prof. G. C. Foster presented the Report 

 of the Committee appointed to investigate Siemen's Electrical 

 Pyrometer. The Committee had principally confined them- 

 selves to the determination of the constancy of the resistance of 

 the platinum coil at high temperatures. Before the instrument 

 can give perfectly concordant results it is absolutely necessary 

 that the coil should be heated and cooled a great number of 

 times. As some further alteration in the instrument was con- 

 templated, the Committee recommended that a further applica- 

 tion should be made to the Association in order to continue the 

 investigations. In the discussion which followed, Mr. Dewar 

 suggested the employment of a spectroscope with a compound 

 prism of quartz and calc spar in the measurement of high tem- 

 peratures. 



Prof. Williamson read the Report of the Committee for Superin- 

 tending the Monthly Report on theProgressof Chemical Science. The 

 meeting cordially testined to its sense of the value of the Chemical 

 Society's work in furthering the spread of chemical knowledge 

 by the publication of its admirable series of abstracts of chemical 

 memoirs published in the leading journals, l^r. Williamson 

 assured the .Section that the movement was rapidly becoming 

 self-supporting, and that in a few years it would be no longer 

 necessary to request the Association to supplement the funds at 

 the disposal of the Chemical Society for the jjurpose. 



Mr. Dewar described some experiments on the determination 

 of the specific heat of carbon at high temperatures. The 

 method of calorimetric measurement differed in no essential 

 particulars from that usually employed. The temperatures em- 

 ployed were those of boiling zinc (1040") and of the oxyhydrogen 

 blowpipe which Mr. Dewar, by the method of Poullct and 

 Deviile and Troost, found to be about 2200' C. Between 

 o— 1030 the mean specific heat of carbon was found to be o'32, 

 between o - 2000 upwards of o'4. Mr. Dewar explained the 

 variation in the temperature of the oxyhydrogen flame as ob- 

 tained by Bunsen himself by the diflerence of pressure under 

 which the combination of tlie two gases occurred in the two sets 

 of experiments. His results on the specific heat of carbon in 

 the main agree w'ith those recently published by Weber. 

 Starting from the difference in the heat of combination between 

 carbon and oxygen to form respectively carbon dioxide, and 

 monoxide, and making a certain assumption for the latent heat 

 of carbon, Mr. Dewar arrives at the conclusion that the boiling 

 point of carbon cannot possibly exceed Sooo' C, and in all 

 probability is somewhat near 7000° C. 



