444 



NATURE 



[Sept. 9, 1880 



45 feet. It thus appears that the rate of increase in this pit is 

 more rapid as we go deeper. The greatest depth in Sir \Vm. 

 Fairbairn's observations was 685 yards, or 2,055 f^^t, and the 

 temperatiire which he found for tliis depth was 754°, vvhich 

 agrees to half a degree with the observations now reported. 



The committee have to express their regret at the loss of two 

 of their colleagues — Prof. Clerk Maxwell and Prof. Ansted — by 

 death, during the past year. 



Report on the Ultra- Violet Spectra, by Prof. A. K. Huntington. 

 — The physical portion of the report was read in Section A. 

 Before the Chemical Section Prof. Huntington drew attention 

 to the following points : — The work of former experimenters on 

 this subject is of great interest. The late Dr. Miller, in his 

 experiments, was obliged to conclude that no connection could 

 be drawn between the chemical composition of a substance and 

 its power of absorbing ultra-violet rays. His method of experi- 

 mentation, however, was deficient, inasmuch as he used layers 

 of varying thickness, and in every case employed saturated 

 solutions. His sub5tances were not so pure as is necessary in 

 such an investigation. 



Dr. Miller also investigated the absorption of the ultra-violet 

 rays by reflection from polished metal'ic surfaces. The results 

 obtained were that gold shows almost total reflection; next best 

 is burnished lead. Other metals present a greater or less al)- 

 sorption. Prof. Stokes' results confirm Dr. Miller's. His pro- 

 cess differed from that of Dr. Miller, inasmuch as he passed the 

 light through a layer of the solution of the substance under ex- 

 periment on to a fluorescent screen, while Dr. Miller photographed 

 the spectrum. His results were of great value, and from a 

 chemical point of view it is of interest to note that glucosides 

 and alkaloids have great absorptive power, and that on addi- 

 tion of acids absorption begins somewhat later than in presence 

 of an alkali. 



In 1874 Mr. Sorby constructed a spectroscope with a fluor- 

 escent eyepiece, and was thus able to observe the spectra directly. 

 His results, though valuable, are vitiated by the impurity of the 

 material he used. 



Mention must also be made of experiments by Prof. Cordieu, 

 who experimented on the influence of the atmosphere in cutting 

 off rays on the ultra-violet end of the spectrum. 



Prof. Hartley, one of the members of the Committee, has 

 recently experimented on this subject, and some of the results of 

 his re-earch have been communicated to the Royal Society. His 

 experiments, made with an improved form of Dr. Miller's 

 apparatus, have led to interesting conclusions. He has found 

 that monatomic alcohols of the methyl series exhibit little or no 

 absorption. The first of the series, methyl alcohol, is, when 

 pure, quite as " diaph.inous " as water to invisible rays. Fatly 

 acids, containing the same number of atoms of carbon as the 

 alcohols to which they are related, have a higher absorptive 

 power. Increased complexity of the molecule causes increased 

 absorption. All members of the benzene series, in fact all 

 bodies whose constitution is best expressed by the "ring- 

 formula," give absorption-bands of great intensity ; the hydro- 

 carbons themselves, however, occupying the lowest position in 

 this respect. Isomeric bodies of this group differ widely in their 

 spectnim, which thus affords a convenient means of identifica- 

 tion. Doubly-linked bodies, such as ethene, propene, anylene, 

 give no absorption-spectrum ; and in fact the ring-form appears 

 to be a siiie-i/ud-noit, for the terpenes and camphor do not absorb 

 ultra-violet rays. 



The intensity of the absorption-bands of naphthalene and 

 anthracene is remarkable ; a solution of I part of the latter body 

 in so million times its weight of acetic acid may still be 

 recognised. 



On the Spectra of Metalloids, by Dr. A. Schuster, F.R.S.— 

 The author staled that he had considerable difficulty in 

 distinguishing the spectrum of an element from that of a com- 

 pound. For example, the familiar spectrum of a Bunsen's 

 flame is ascribed by some to carbon, and by otiiers to a hydro- 

 carbon, the argument in favour of the latter view being that the 

 temperature of the flrme is not sufficiently high to volatilise 

 carbon as such. The reply to this argument is that during its 

 passage from its compound with hydrogen to CO or COj, the 

 element carbon is actually liberated, and then exhibits the band- 

 spectrum ; and in confirmation of this theory it has been noticed 

 that gas impregnated with a s.alt of a metal such as copper or 

 iron, gives in the Bunsen's burner the true metallic spectrum 

 and not the spectrum of a compound. The same argument 



applies here, for the metal is actually liberated during its 

 passage from (say) the chloride to the oxide. Besides, the band 

 spectrum is seen still more effectively when cyanogen is burned, 

 even when dried as perfectly as possible. This band-spectrum 

 is seen in the sun's rays, and it is highly improliable that 

 cyanogen should be able to resist such an enormously high 

 temperature. 



The author then considered the question : — Why should an 

 element give different spectra at different temperatures? Bands 

 are characteristic of compounds, and at low temperatures ele- 

 ments show a banded spectnim. At higher temperatures such 

 spectra become simpler, and the evident conclusion is that 

 complex molecules of the elements are dissociated into those of 

 a simpler order. Tliis view is rendered highly probable by the 

 fact that the spectrum of mercury is a constant one, and that 

 no known increase of temperature alters its character ; now, 

 assuming the molecule of hydrogen to consist of two atoms, that 

 of mercury consists of a single atom, and it is evident that no 

 simplification is possible. 



The change of the spectra of chlorine, bromine, and iodine, 

 as the temperature is increased would seem to corroborate Prof. 

 Victor Meyer's recent conclusions with regard to the molectUar 

 complexity of these elements. 



It was also suggested that the spectrum of an element might 

 vary according to the compound from which it is liberated. 

 Were it possible to decompose carbon monoxide and dioxide, 

 and to obtain the spectrum of the single carbon atoms which they 

 contain, it would probably differ from the well-known banded 

 spectrum of carbon which there is reason to suppose is that of at 

 lea^t a two-atom molecule. 



Mr. W. Chandler Roberts pointed out that Prof. Wiedemann 

 has undertaken measurements to ascertain whether a change of 

 temperature takes place during .alteration of the spectrum, and 

 hoped that interesting results would be obtained. 



Report of the Committee on Erratic Bloch, presented by the 

 Rev. H. W. Crosskey. (Abstract.)— Although the destruction 

 of erratic blocks is proceeding with considerable rapidity, the 

 Committee were able to report the discovery and preservation of 

 some important specimens. 



One of the most remarkable blocks of Shap gr.anite yet 

 obssrved is described by Mr. J. R. Dakyns at Seamer Station, 

 near .Scarborough. It measures roughly 5 ft. S in. X 4 ft. 10 in. 

 X 4ft. 3 in., and was fairly imbedded in gravel, forming the 

 summit of a well-marked terrace 225 feet above the sea-level. 

 This boulder is specially interesting in that it is the only boulder 

 of Shap granite in the neighbourhood whose position in the beds 

 is known ; and this position shows that at the age assigned to 

 the gravels (which is a comparatively recent one) icebergs must 

 have been floating about. It has been preserved in the garden 

 of the Station House. 



The report records particulars of boulders discovered in the 

 neighbourhood of Urmston, near Manchester, and also of a large 

 number both of isolated boulders and groups of boulders 

 observed in Leicestershire by Mr. J. Plant. 



Mr. Pengelly furnishes a very interesting part of the report in 

 an account he gives of some transported blocks and accumula- 

 tions of blocks Aihich he has observed in South Devon, the 

 transposition of which it does not seem altogether possible that 

 the action of water alone could have effected. A block of 

 greenstone occurs in the village of Kingston, South Devon, 

 measuring 4X2X2 feet, and weighing upwards of a ton. 

 There is a mass of greenstone figured on the map of the Survey, 

 extending to about a mile we-t-north-west of Kingston, where it 

 makes its neare^t approach to the village. Blocks of quartzite 

 have been found in great abundance in the parishes of Diptford 

 and Morlcigh. They can be traced to their source on the higher 

 levels of the neighbourhood ; a bed of quartzite identical in 

 character with the travelled blocks being interbedded conform- 

 ably with the ordinary slaty Devonian rocks of the district. 

 There can be no doubt that the blocks have been transported 

 from south to north, and from higher to lower ground. The 

 gradient, however, is very slight, and as almost all the blocks 

 are very angular as well as large, it is difficult to suppose that 

 their tr.insporlation was the result of nothing more than running 

 water. 



A block of greenstone occurs near Diptford Court, weighing 

 fully I '75 ton. A mass of igneous rock apparently of the 

 same kind is found at a distance of five miles due south of the 

 l.oulder, and another about the same distance north. 



The blocks locally termed in South-Western Devon "Whita- 



