( 502 ) 



Physics. — '"Mi'tli(>il< mul ii jtixiratn^ iiscil ni tlu' ri-jfot/i')//': lahoni- 

 torij. III. ll'ifli-< of rcni inn toi'iii iiihI cinishiiil l(ni' li'in jii'i'illiiri's 

 ill llii' ciiiitshtt." ( 'oinmiiiiicalioii N". K\ IVoiii llic |ili\sical 

 lal)uriil(»r\ al liei<leii In I'lol'. II. K \Mi;in,i\(;ii Hnnks. 



(( '.oiiiiiuitiic-iilal in llic luc'ciiii;-; ol' Uceoiiilun' '11, I'JO^. I 



§ I. I)\ means <»(" the crvoslal descrilxMl in \S S. ('omin. 14. I )('C. 

 "1)4, ami § li, (Nmim. 51. Se|»l. "!)ll we can (iWlaiii a Walli (»!' 

 licjiielied ,ti,'as wliicii is .sjiui oil" (Vom llie alnKtsphci-c and \n)\\>. at 

 ordiiiarv or diniiinslied pi'es.smx'. In sncli a halli llie tcniperatnre 

 is snIïicientU nniloian and eoiislanl lor niaiiv experinieiils and inea- 

 sm-eiiienls. It' \vc use almost pure uases and if the exaporaletl uas 

 is renularlv i-eeoiideiised liv means of a eoni|n-essi(in appai-alus. 

 which as descriheil in ('omms. J4. Dec. "04, 53. Sept. 'W and 54. 

 Jan. (H), does nol contaminate the ua'-. the hath niav he maintained 

 as lonu' as we w isli. The o[»ei-alion-- in the hath itself a^ well as the 

 addition of the li(pielied ;^as can he watched ihroniiii the oliscrvinu' 

 IU'lasses. \ acunni glasses are nol ropiircd so that similar crvostats 

 ma\' he constructed foi' measnrinLi' apparatus of anv (linieii--ions. 

 Uefoi-e l(»n,U' we shall descrihe a crvoslal where the uas apparatus 

 and the hath are moi-e inde|)endenl. 



1 was led to desci'ihe the form of the crvoslal. as it occurs in 

 ('omni. 51, throuLih the comminiicalion of the results for the di-eleclric 

 conslanis of li(piid .uases. (Comni. 52 Oct. '!)!)). Ibi- which ineasui-emenis 

 onh the tem|)eralures of — IM) ( '. or iS'i' ( '. were i-e(piire(|. l''(»r 

 other measurements, however, a measin-inu' ap|»aralus. (uice ininier>cd 

 in lh(> crvostat, has heen used al the Aviiole raniie of tempeiaiures 

 helween, — 23^ ('. (hoilin.i;- ]»oinl of melhvl chloride at ordinaiv pi-es- 

 sure) and — 2 10^ ('. (Jiitrugon at reduced |)ressurel. iiiveii l>v nielhvl- 

 chloride mirous-oxide, ethylene, meihane, o.xyucu and julro.ucii as they 

 were successi\-ely adndtled into the crvoslal. 



h'or a loni;- lime improxemeuts ha\e heen niaile iji this crvoslal 

 hv means of which we can attain a much urealer uinformity and 

 constancy in the lem|)erature, vvhile rc^ainiii.Li- the afoi-e-inenlioned 

 advantages. A desci-iptioji of these alleralioiis has now ix'cmue iieces- 

 sary in ordei- to Judge of the accuracy of the temperature readings 

 in the i-esults from various ineasni-emenls where we have axailed 

 ourselves of these im|n-ovements. 'I'hese measurements will he treated 

 in the next communicaliojis. Anu)ng others 1 nu'Jition here those 

 hearing uj)on the isuthermals of diatomic gases (Comnis. 61) .March '01 



