066 



UEroiiT — 1884. 



ii; 



>:M'f 



ill! 



u 



examination of a sijoctrmn l)y Lockyer'.s inutliod, to jiriHlict tlio clianpfs wliicb ji 

 will iindorji'O, either on iiltcnition of t('ni])eriitiiri', or i)y an inerfusc or dccri'iv-e di' 

 quantity. Thcvo apix'ars tobo no tlieorotioal <lillicnlly in ussMniin^ tlial the vcluiiv, 

 intfn.sity of the linos may vary when tiin tcnuK^ralnro is allcrcil, and the niolc( nhir 

 theory of <rasi's rnrnislics us with a jtlaiusihle fxiihination of tlio ('orrcsnonilia};- 

 ohan^'o when tin' relative quantities of the luminous elements in a mixture arc 

 altered. Jjoclvyer has proposed a ditlerent explanation of the facts. Aeeonlliiir to 

 him, every clmn^'e of relative intensity means a correspontlin^' ehan;.'ool' molecular 

 eomplexity, and the lines which we see stronir near the jioles, would Lear the siuui' 

 relation to those wliieh arc; visible throufrhout the Held, as a line spectrum hriips t,) 

 a band .«])eflrum ; but then almost every line mnut be due to a dillerent luoluciilar 

 fjfroupinj!:, a conclusion which ia scarcely capable of bein{? upheld without very 

 copent proof. 



Tiie exainination f>f the al)soi'ption sjitjctra of salts, saline and orf^anic li([ni(ls, 

 first by (iladsTinie, and al'terwards by l>unsen,and hy lius.scll, as Avell as by llaitlrv 

 for the ultra-violet, and by Abney and lasting' J'or the infra-red rejiion, have led lo 

 interesting results in relation to molecular chemistry. Thus Hartley linds that in 

 some of the more complicated aromatic conipoiuids, definite absorption bands in tlir 

 more refranijfible rejrion are only produced by siitistances in wdiicli tlnve pairs of 

 carbon atoms are doubly linked, as in the ben/.eiie ring, and thus thi^ means of 

 ascertaining this double linkage is given. The most renuirkabhi results oljtiiiin'il 

 by Abney and Festing show that the radical of an organic body is always repre- 

 sented by certain w(dl-marked absorjition Itantls, dill'ering, however, in positimi, 

 according as it is linked with hydrogen, a halogen, or with carbon, oxygen, nr 

 nitrogen. Indeed, these experimenters go so far as to say that it is highly pn- 

 bable that by this delicate mode of analysis the ]iy]inthetical position of any hydm- 

 '^en which is replaced may be identified, thus ]ioiuting out a method of ]ihysic;il 

 orientation of which, if confirmed by other observers, chemi'-ts will not bo slow 

 to avail tliemselves. This result, it is interesting t(j learn, has been retidereil nmrr 

 than ])robalde by the recent important researches of Perkin on the cdiniuutioii 

 between the constitution and the optical properties of chemical compounds. 



One of the noteworthy features of chemical ])rogress is the interest taken l)v 

 physicists in fundamental questions of our science. We all reuunuber, in the first 

 place. Sir William Thomson's interesting speculations, founded u])on physical \)hv- 

 nomeiia, resjieeting the probable si/e of the atom, viz., ' that if a drop of wativ 

 were magintied to the size of the earth, the constituent atoms would be larger tliim 

 .small shot, but smaller than cricket balls.' Again, llelmholtz in the Fin'adiiy 

 lecture, delivered in 1881, discusses the relation of electricity and chemical eiier;:y, 

 and points out that Faraday's lawof electrolysis, and the modern theory of vakncy, 

 are both expressions of the fact, that when the same quantity of electricity pajx.s 

 through an electrolyte, it always either sets free, or transfers to other combina- 

 tions, the same number of units of alHnity at both electrodes, llelmholtz linUnr 

 argues, that if we accept the Daltonian atomic hypothesis, we cannot avoid \h- 

 conclusion tliat electricity, both positive and negative, is divided into elementary 

 portions which ])ehave like atoms of electricity. He also shows that these ciiarL'c'= 

 of at(unic electricity are enormously large as compared, for example, with tlio 

 attraction of gravitation between the same atoms; in the case of oxygen ar.d 

 hydrogen, 71,000 billion times larger. 



A furtlujr subject of interest to chemists is the theory of the vortex-ring con- 

 stitution of matter thrown out by Sir AN'illiam Thomson, and lately worked out 

 from a ch(>mical point of view by J. J. Thomson, of Cambridge, tie finds tlip.t 

 if one such ring be .supposed to constitute the most simple form of matter, say the 

 monad hydrogen atom, then two such rings must, on coming into contact with 

 nearly the same velocity, remain enchained together, constituting what wo know a-; 

 the molecule of free hydrogen. So, in like manner, systems containing two, tbrec. 

 and four such rings constitute the dyad, triad, and tetrad atoms. IIow far tlii^ 

 mathematical expression of chemical theory may prove consistent with fact reiuaiii> 

 to be seen. 



Another branch of our ,«cience which has recently attracted much experimental 



