August 3, 1893] 



NA TURE 



to a maceration of the respiratory muscles, 'producing as- 

 phyxia 



Wiedemann's Annalen der Physik und Chemie, No. 7. — On 

 the specific heats of glasses of various compositions, by A. 

 Winkelmann. The specific heats of the various constituents of 

 diflferent glasses were calculated or experimentally determined, 

 and those of the glasses made up of them were calculated by 

 Wostyn's law, according to which a specific heat of a compound 

 is obtained by adding together the products of the specific heats, 

 the atomic weights, and the number of atoms of the elements 

 contained in the compound, and dividing by the sum of the pro- 

 ducts of the atomic weights and numbers of atoms. On com- 

 paring the values thus calculated with those found by experiment, 

 it was found that they agreed to within one per cent. — On a sur- 

 face connected with the electric properties of tourmaline ; 

 thermodynamics of tourmaline and the mechanical theory of 

 muscular contraction ; and molecular theory of piezo-electric 

 and pyro-electric phenomena, by E. Riecke. The author makes 

 the attempt of formulating a thermodynamical theory of muscu- 

 lar contraction, and investigates its connection with the pyroelec- 

 tric phenomena of tourmaline. He arrives at a formula in which 

 the state of the muscle can be expressed by two variables only, 

 the temperature and the tension. — Concerning the theory of 

 electric oscillations in wires, by A. Elsas. The author shows 

 that the Hertzian oscillations may be completely explained on 

 the older electromagnetic theory, without reference to Maxwell's 

 amplifications. He does not contend that Maxwell's theory is 

 superfluous, but finds out how far the older theory is capable of 

 proceeding without having recourse to Maxwell's conceptions. — 

 Objective representation of Hertz's experiments, and the high 

 tension accumulator, by L. Zehnder. A collection of practical 

 hints for the performance of oscillation experiments by means of 

 the 6oo-cell Plante accumulator. — Contributions to the theory of 

 secondary batteries, by Franz Streintz. With comparatively low 

 current densities, the resistance during discharge attains a maxi- 

 mum. As the current increases, the resistance slowly falls to a 

 value equal to that in open circuit, and falls still further at higher 

 current strengths. —On the determination of the length of a 

 solenoid, by F. Himstedt. Contrary to Heydweiler's opinion, 

 the length and radius of a solenoid as determined by its electro- 

 magnetic effect are not appreciably diflferent from their geomet- 

 rically calculated values. 



In the Botanical Gazette for June Mr. R. H. True has a paper 

 on the development of the caryopsis, which supports the ordinary 

 view respecting the formation of the fruit in grasses. Prof. 

 Atkinson continues his account of the biology of the organism 

 which causes the tubercles on the roots of LeguminosEe. 



In the Journal of Botany for July, Mr. A. B. Rendle de- 

 scribes and figures a case of the production of tubers within a 

 tuber in the potato. Yet two more "species" are added to 

 the long list of British Hieracia by Messrs. E. F. and W. R. 

 Linton, // enstales and orcadense. 



In the Nuovo Giornale Botanico Italiano for July is a paper by 

 Sig. E. Baroni on the anomalous genus Kohdea, which he pre- 

 fers to place in the order Liliaceae and tribe Asparagece, rather 

 than in the Aracea;. The minute structure of Rohdea japonica 

 is described, and the mode of pollination, which appears to be 

 effected partly by insects, but largely by snails, and even by 

 spiders. 



The Bulletino della Societh Botanica Italiana, Nos. 5-7, are 



largely occupied by papers chiefly interesting to Italian 



botanists. In a Idition, ,Sig. A. Baldacci has some observations 



on the sympodial branching in Symphytum and in other 



Borraginese, and on the mode of branching in the 



Apocynacete, which appears to be also sympodial. Sig. U. 



Brizi enumerates the fossil Mu«ci and Hepaticae found in a 



locality within the Roman territory. .Sig. C. Acqua describes 



the mode of formation of the wall in the growth of the poUen- 



, tube of Vinca major, which presents a strong resemblance to 



1 that described by Buscalioni in the aerial hairs of Lavatera. 



I Sig. C. Massalongo has several papers on galls. 



SOCIETIES AND ACADEMIES. 

 London. 

 Royal Society, June i.— "On the Colours of Sky 

 j Light, Sun Light, Cloud Light and Candle Light." By 

 'Captain W. de W. Abney, C.B., D.C.L., F. R.S., P.R.A.S. 



NO. 1240, VOL. 48] 



The author has made several comparisons of the above lights 

 throughout the different parts of their spectra, and has been 

 able to verify their correctness by means of templates rotating 

 in the spectrum of electric light, as described in Part II. , 

 "Colour Photometry," Phil. Trans., 1889. It seemed, 

 however, that it would be useful if the colours of these lights 

 could be expressed in single wave-lengths, together with the 

 amount of added standard white light, the latter being ex- 

 pressed in terms of the luminosity of the dominant colour, in 

 accordance with the method brought before the Royal Society 

 in Proc. Roy. Soc. , 1891. 1 



When measuring light from the sky, a beam from the zenith 

 or other desired part was reflected through a blackened tube into 

 a darkened room in which the colour patch apparatus ("Colour 

 Photometry," Abney and Festing, i886) was placed, and the 

 image of the end of the tube was focussed on to the front sur- 

 face of a cube, the front surface of which was coated with zinc 

 while, its background being black velvet. The patch of colour 

 from the apparatus was also thrown on the cube. A rod placed 

 in the paths of the two beams enabled the sky light and the 

 spectrum colour to be examined side by side. The slit in the 

 spectrum was an adjustable one so that any intensity of colour 

 within limits would fall on the cube. A beam of white light 

 reflected from the first surface of the first prism was again re- 

 flected from the surface of a thin prism on to the cube, a rod 

 placed in its path cast a shadow on that part illuminated by 

 the sky light, and by suitable adjustment the boundaries of the 

 two shadows were caused to exactly coincide. The colour was 

 thus diluted with white light, and rotating sectors, described in 

 other papers, being placed in the path of the white beam, 

 enabled the dilution to be regulated. 



Sky Light. — On June 27, 1892, at 2.30 p.m., the sky was a 

 good blue, but not a dark blue, and perhaps rather milky. The 

 slit was moved into the part of the spectrum which appeared to 

 be near the dominant colour. The colour was diluted to ap- 

 proximately the required amount. The slit was shifted and the 

 dilution altered until the two colours made a perfect match. It 

 was found that on the standard scale of the spectrum the domi- 

 nant colour was represented by 28'6, which is \ 4800. The 

 mean value of the sector aperture was 32°, and recollecting that 

 the sectors are double sectors the comparison has to be made 

 with 180°. The next operation was to compare the luminosity 

 of the whole beam of white light with that of the colour. The 

 sectors still remained in the white ; the sky light was cut off, 

 and the rod altered till the colour and the white were alongside 

 each other with the boundaries of the shadows touching. The 

 luminosities of the two were compared, and it was found that 

 the aperture of the sector was 14°. As it required 32° of white 

 to make the dilution of the colour, it follows that 32/14, or 

 2 286, parts of while were required to dilute I part of the blue. 

 This may be expressed thus — 



Sky light = K 4800 -1- 2'3W. 



On July 4, 1892, at midday,(he same procedure was adopted, 

 and the dominant wave length was again \ 4800. In this case 

 the amount of added white was thus — ■ 



Sky light = K 4800 J- 3-lW ; 

 in other words, the sky was more milky. 



At 4 p.m. on the same day the sky to the east, and about 

 30" above the horizon, was evidently slightly greener, and it 

 was found that the colour agreed with scale No. 29'6 or \ 

 4834, and that it required three parts of white to be mixed 

 with it. 



Sky light = X 4834 + 3W. 



On other days, when the light of the portion of the sky near 

 the zone of maximum polarisation the dominant wave length was 

 found to be between these two limits, and was never found 

 bluer, and the smallest admixture of white light was found to 

 be I '9. 



From these measures it may be concluded that the dominant 

 colour of a blue sky is A 4800. 



Amongst artists it is not uncommon to employ cobalt to 

 render this colour, and in many instances this is mixed with 

 Chinese white. 



The dominant colour of cobalt was found to be at scale No. 

 29, or \ 4812, when illuminated by ordinary day light, whence 

 it seems that, as far as colour is concerned, it is singularly fit for 

 the purpose. 



Sun light was compared in the same manner, but the beam 



