March II, 1880] 



NATURE 



445 



still brighter ihau Venus at i's maximum brilliancy, lue a 

 suddenly appearing flame in a white colour. The bursting-point 

 I could sharply determine I J" below the middle of the line 

 a Pise. - y Celt, in the given direction ; the mistake being 

 not greater than one degree. 



Accident having favoured me, looking sharply as I was in the 

 direction of the phenomenon, my observation will, perhaps, have 

 some importance, if positions of the same fire-ball have been 

 taken by English ob-ervers. II. T. II. Groneman 



Groningen (Netherlands), March 4 



Sunshine 



It may interest your readers and the Fellow s of the Meteoro- 

 logical Society to know that "the sun is always shining some- 

 where," even though we have so little demonstration here. In 

 a letter received from Adelaide, from a reliable observer, I note 

 the following : — 



"Last Tuesday, January 20, was a cooker ! 1 1 3' '■ 5 in the 

 shade, and 172" in the sun, the highest ever registered here ; the 

 latter being within 40 of the boiling-point of water." 



Chas. Coppock 



Grosvenor Road, Highbury New Park, March 5 



Lines of Force due to a Small Magnet 



Referring to my communication in Nature, vol. xxi. 

 p. 370, the value of y, for which the radius of curvature (/<) is a 

 maximum, should have been_j- = '317 C, not '432 Cas stated. 



Glasgow, February 27 John BUCHANAN 



Artificial Diamonds 



I read with great surprise a paragraph in Nature, vol. xxi. 

 p. 409, referring to an investigation which I am now making 

 on the artificial production of various crystalline forms of carbon, 

 and I write to disclaim all responsibility for statements which 

 have been published without my knowledge or consent. 



R. Sydney Marsden 



University College, Bristol, February 27 



[The correspondent who sent us the paragraph in question sent 

 it in good faith, believing the matter to be to that extent public. 

 —Ed.] 



Jas. Rock. — The galls which your gardener found growing 

 on the root of an oak-tree, about six inches below the surface of 

 the ground, arc probably galls produced by Biorhiza aptera. 



J. W. Wyatt. — The appearance in the specimen of a decayed 

 ash bough is caused by the mycelium of Hclotium aruginosum, 

 Fr. [= Peziza aruginosa, Fr.]. See Cooke, " Handbook of 

 British Fungi," pp. 70S, 709; "Official Guide to the Kew 

 Museums," p. St. 



PICTET' S PROPOSAL TO DISSOCIATE THE 

 Ml ' TAL L OIL) ELEMENTS 



'THE task set before me is to expound in as simple and 

 - 1 intelligible language as possible the remarkable 

 train of reasoning which has led M. Raoul Pictet,of Geneva, 

 to the conclusion that the so-called metalloids are really 

 not elementary bodies at all, but capable of dissociation 

 into simpler forms. During the last two years M. Pictct 

 has published several important memoirs upon different 

 branches of thermo-dynamics, and has, as is well-known, 

 in his researches on the liquefaction of oxygen and of 

 hydrogen shown the fruitfulness of the ideas which have 

 thus occupied him. He is at the present moment engaged 

 upon a large volume entitled Synthase de la Ckaleur, a 

 work in which it is sought to deduce all the known laws 

 of heat from thegeneral principles of theoretical mechanics, 

 by finding true mathematical definitions for the quantities 

 which hitherto have been usually expressed as simple 

 experimental matters. Thus the terms "temperature," 

 "specific heat," ''latent heat," Sic, are capable of exact 

 definition in a manner which enables the relations between 

 them to be investigated analytically. These relations 



thus investigated are found by M. Pictet to be capable of 

 experimental verification, and the complete acccordance 

 of deduced theory with observed fact justifies him in 

 giving the name of Synthesis of Heat to this new advance 

 in thermo-dynamics. 



To understand aright the views of M. Pictet with 

 respect to the possible dissociation of the metalloids we 

 must notice briefly the fundamental points of his theory 

 of heat. If the atoms of a body are in absolute rest and 

 equilibrium, their temperature will be at absolute zero. 

 If however, kinetic energy is imparted to these atoms 

 and they are set vibrating, the temperature of the body 

 will be represented by the mean amplitude of the oscilla- 

 tions, and the total quantity of heat in the body will be 

 the quantity of energy thus imparted. 



Now the great decomposing force in nature is heat. 

 It is heat which changes solids to liquids, liquids to 

 vapours. Heat breaks up chemically combined substances 

 and reduces them to simpler forms. It is quite certain 

 that the limits of the power of the chemist to decompose 

 the substances that pass through his hands are those 

 which correspond to the .temperatures which he can 

 produce in his laboratory. We shall explain at a 

 later portion of this article how this comes to be the 

 case. Yet there are in nature temperatures far more 

 elevated than the highest artificial temperature. To 

 take the most striking example, the surface of the sun 

 must be enormously hotter than even the hottest of 

 the electric arcs in which even the most infusible of 

 metals is vaporised. We know this upon evidence which 

 accumulates evety day, and of which the most important 

 is that afforded by the spectroscope. The researches of 

 Kirchhoff and J. W. Draper, and the later work of 

 Cornu, Mascart, and Lockyer, establish incontestably 

 that the radiation emitted by a glowing substance varies 

 with the temperature of the substance, and that at higher 

 temperatures new rays of shorter wave-length and more 

 rapid oscillation appear, while the intensity of all the 

 emitted rays is also greater. The solar spectrum is much 

 more rich in violet and ultra-violet rays at the more 

 refrangible end of the scale than the spectrum of any 

 artificially heated substance. The irresistible conclusion 

 is that its temperature is far higher. 



But the spectrum of the sun when scrutinized with the 

 most elaborate skill and knowledge reveals another very 

 striking circumstance. A large number of the substances 

 regarded by the chemist as elements have now been 

 recognised by the characteristic absorption lines of their 

 spectra as existing in the heated matters surrounding the 

 sun. The researches of Mr. Lockyer show that nearly 

 forty of the metals are thus to be detected. But not a 

 single metalloid is thus discoverable. Indeed so marked 

 is their absence that the presence of hydrogen in such 

 creat abundance is held by no less an authority than Mr. 

 Dumas to be a convincing proof that hydrogen is a metal 

 and not a metalloid. It is true that Mr. Henry Draper 

 of New York, has announced the discovery of bright 

 lines corresponding to oxygen amongst the dark absorption 

 lines of the solar spectrum : but it is far from certain 

 whether the coincidence he has pointed out is real or 

 apparent only, and all other evidence points to an adverse 

 conclusion. 



Putting together these two capital facts of solar spectro- 

 scopy, the irresistible inference is that the surface of the 

 sun is too hot for metalloids to exist there ; or in other 

 words, its temperature is higher tlian the temperature of 

 the dissociation-points of the metalloids. This term 

 dissociation-point is justified by analogy with the terms 

 boiling-point and melting-point, with which we are 

 familiar, and with which we associate the notion of 

 definite temperatures. 



Let us examine, following M. Pictet' s fundamental 

 principles, how far this analogy can be followed out and 

 Justified. Those fundamental principles are that in hot 



