;76 



NATURE 



[May 



. i 



tinn •<! «h»' ilu-f>rv nf thf aether. As rctfnriU mathc- ! 

 .ce is s.'i\ 



,, V , , ■ i>. II, a»; wfll .. 



. - 1<, ihr oi i;^iii,il ini'iiii .11 - ; ' li' 

 . iin)ji.i i.iiil ;i(l\ .iii< '■-. u iiliout ■ iii-- 



^11111(1. nfl\ .1(1' c|ii.ii.' I., dclin'- !; !v in 



:i-l..i ii .il - iiiiit;, lh.it t" in;; ll.. 



. i I.I .1 V, (.1 Iv "I lllis 1\))... 



I un-ihinl- i.t 111. 1m. m1, ,,i. (|.\<.N (1 1.. ill' ).i I i"<i I 

 : ; ;ii!L; liuin I )i ■^( . 1 1 1 1 - I'. \ 1 .1 X w I 11 . \\ >\ nU'^t \ 



ihi- will |.ii.li;ilil\ 1h \\\>- mmi \.ilii.il>li pcr- 

 ; 111 .mis'nii; m...i1.; vOiiih i- '..! ii-il\ :in r-vil,].- 

 1 >: W 1:11 1.;].. I ir,J.. - ■■ ;■ idililiuii to ill.' 



ii-.ii.i\ i-t ilii l.iu i.i lii I t! I .-;.! ; 11 .iMi.ulii.n l)il\\<iii 

 •ui. (IhiiLlid |i.iiii( l.-v. 'I 111 l.iu (it in\iT-f -(.|u.in- i.f 

 'ill' (ii^i.iiiic is coininonh :i-('iilircl to ( 'luili hiiIp. on 

 .uTdunt (.t \\\^ ciirrci \ciitir.iliiin li\ mcin-. i.t ihc 

 torsion h.i!;tncr |i7.'<5l. W'iitn the risi:ii clu- ut ilic 

 Hon. llcnrv ( 'avnidi-vli ucir i-diii d Kv M.iwmII in 

 i.^7<i. il w.is -i-i-ii thai ilii- --.inir law had hirn i vi.il.. 

 li^-hrd h\ a dirifiriil iiifihiKi a~. iari\- a-. 177.;; on 

 ;. !i iiiiiL; lo I ail\ lili iMluii', --aril a-- ^'ou^t;'-. " I .1 1- 

 llili s," il a|i|iraicd ihal lln" u 1 1| uihl i ^hii I \\(ifk ol ('a\in- 

 (li>li was tjuilr unknown lo hi> ronIiin])<irariis. | )r. 

 Whiltalvcr dincis aiiiniion to a still earlier statement 

 in I'l it silcA 's ■' Hisior\ ol l^li'dricity," published in 



7117. It appears thai Pi'ii>lli'\-, tollowinj^ l-'ranklin. 

 had made fxpiiimi-nU which showed that, wlini a 

 hollow nirtallii- \issrl j, ilrctrit'ii-d, ilnre is no chari;!? 

 on the inticr suifaci'. an. I nr> iln-tric force in the air 

 ::isldi-. Pricsiicx ihi-n contiiun-s: 



■Max wf not inter iVoiii this r\])crinicnt that the 



nraction ol clrctricitx is sul.ji-ct to the sann' laws ; 



\:tii that ot i^ra\ilation, and is therefore according,' I 

 "o the sipiares <if tlu- distances ; since it is easily 



deniunstrated that were the earth in the form of a | 



<hell. a body in the inside of it would not he attracted : 



to one side more than another?" ' 



The chapter on elastic >olid thiories covers an iin- 

 |H>rlant period. Cauchy. who was fust in lln' field, I 

 obtains full credit for his various tlnories; .ilihoui^h ( 

 one sees how his work failed to stimulate Liter | 

 writers, esjieciallv <^f the En^lii^h school. Dr. Whii- 

 takei- reni,irl<s th.it his point of \iew in the e.irlier 

 theorii s ,ippi:iis to ha\-e heen :( livi-n t he equal ions of [ 

 vibration ot .in elastic solid, what Ixnindarv condi- I 

 tions must be used in order to obtain hresnel's ri suits? i 

 It was Green who first showed that with a properlv \ 

 localis(.d ener^v functi<in. the Lajj;rani;ian method | 

 gave not only tlie equations of motion, hut ;d<o the i 

 correct houndar\ conditions. j 



Some attention is p.-iid to the a?ther of (".uicln's i 

 third theory of renection, lietter known as the con- 

 tractile a'ther of Lord Kelvin. The form ^>{ iiiei -y I 

 function used by Lord Kelvin might ha\e hi m ! 

 noticed; .after beginninjj with the ordinary form tor ' 

 an elastic solid, he transformed it, by inteeraiine h\ 

 parts, into a form similar to that of MacC'ull.ii^h's j 

 theory. One would consider this form as i)roiHrlv j 

 localised, not for the contractile aether, but for a 

 medium specified to be rotationally elastic. 



In the later portion of the book niechanical theories 

 are treated further under tlie more modest description 

 ol models of the aether; there are also chapters on 

 NO. 2168, VOL. 86] 



till ftllowtrs of M:ixwetl, Ofl Conduction in ^.Imif.n* 



I lore recent theori* d 



ax\\< 11 ; in par- 



itive motion of 



.1 consideration 



.K of byftlciiKs of nieasui • space and 



. period of the book clo :. the siher 



•d with a (eri.iin degree of substantiality, 



1.. Il ri n! it iii.r, hi- from ordin;ir\ mnlter. In 



^ theory 



■ \ \ 1 1 1 1 1 .1 ].' 1 s iri.uisi- ,ij)j)e.ir> at an 

 ; il forms ,in important and valuable 



■ '1(1 ii.ir.iii\i- study of ih'i.ti. - , •" rh. 



a'thd. ' i . il. ii. 



.ind j. ••. Hall. I'p. .\ + 5 1 v (New !ie 



Macnall. ■, < 'o ; London - M ., •, M! .• . '_ ,j., 



Ltd 



TIN'S i,i.,.i^ !>, pnniarilN inieiii.led lor tii'.-' 

 wisli to recoi^Miise without h.i\ing recc 

 the microscope and then to ungous disease* 



of rulti\-,:ted pl.ints. Disii); .■ given of the 



I cli.ir.icteristics of tl;. destructive 



(. ;:;iil .and \'eL:et.ah|. 'fd in the 



I ill as i- 



lad s, ,1 i 111 us 01 pieveiuioi 

 bulletins c'f the numerous > 



tneiital stations and of the I -^ofi- 



culture have been examine . uthors 



have had the help also of various specialists in read- 

 inj,^ ti\er ilie proofs of certain parts, c,^. Dr. Erwin 

 v. Smith li.is ihus .assisted with :' 

 Dr. L. R. Jones with potato di- 

 Sh(rt. (dear, scientific descr; 

 x.irious life-stages of the sp.Li.s .. 

 plant distases; these are accomp.ani 

 advici .is to the methods to h. st 



I .ich si;|o,. |,y the grower. In ■ in 



ih.ii 1: :h.i onion "smut" .and i inmon 



stall" I •• tin ])otato, and of the v.ai ; .ises of 



th( .ipple. the .account L^iveii is .1 model of what 

 should be provided by the " •■ .■ s.-icn,-,- «ot- the 

 pa.ictical man. Clear direi he 



making and application of funmciues, ul 



information on the subject of spra;. y. 



It would have been well, h. .1 have supplied 



fuller information on the s '■Borde,nux in- 



jur}'." arc ■ -iiaN' he a\(.>i(,i. 



.-.I'e f,i\(n : . iisinfection i.A - 



tormald( h\d( i;,is. and the various methods of soil 

 disiii-'i 1 -Win .an. discussed. It is point. .d ..or ihr.t ili*. 



Kind of such iner.adicibli 

 ihi ii :(ii;i. cowpeii. Cotton, or tobacco wi;-. o-^.a -t 

 "smut." cabb.a.ee 'hlack rot," \c.. may result in a 

 depreciation of 50 per C( m. or more in the 

 value of the land. In d'-adin::: with m.anx- 

 disea- o, 



carna . .- . ; id 



other Iru'' ihors are not content with nv n Iv 



