USS rJ':Tri:iiss(>x, o.x uatku axd ick. 



iho instruniont would bo impracticablo to mo, without tho 

 iini>r(n'(>nuMit. devisod by Scliullor aiul Wjirtlia, viz. to im- 

 nuMsc th(> calorinuHcr in a ^•('ss(>l containiuL:; icc and \)\\vo 

 wator at O". Still tho advaiitajj,(> ot tliis arrangoniont is not 

 i() provciit variations in tlio position of tho niorcury indox of 

 tlu> insininuMit , bul lo make Mkmu (piilo iH\i2,iilar. 



'V\\o variations ari' drchuHMl by sonio physioists to dopond 

 upon llu> vacillations of ilu> atinospluM-i(" ))rossnro, which 

 lo\V(>rs or rais(>s l\\v nu^ltini;' poinl of \\\c ivo, but 1 daro say 

 from lonsj,' (>xporionc'o, tluit \\\c niovcnuMil of tho niorcury 

 <'olunin is in sonio way intiutMunMl l)y llio tcnipcratnro (^f tho 

 ;iir in tlu' rooni, bnt. is wholly iii(lo|)(MidiMit^ i^\' tlu> baronuMric 

 variations. Tho roal i-anso of tho unstoadinoss of tlu> index 

 soonis to mo to Ho in iho impnritios absorbod by tho wator, 

 which bas biHMi krpt boilinu' for almost an bonr in tlu> ^iass 

 rosorvoir by tho lillinii; of tho instiaimont. Thus tlu> ico will 

 bo oxaolly in tho samo condition as tho sanijdo II in tho 

 abovc^ labK>s, vi/, it will possoss no ahsohi/cl// Ji.r<'<l rohiiiic jnst 

 bolow its nudlinj;' i>oint. 'Vho spocitio voUimo of tho ioo in tho 

 instrnnuMit will thns i'orro»spond lo somo point of tho sU>pin.u' 

 brancb oi' Iho rnrvi> 11, s(H> jdatc l?l\ bctwcHMi — O\o,^and()'^ Now 

 supi>oso tho >vator in tho oxtormil vossol to bo oitlior a little 

 l)nror than that o\' tho calorimotor or vioo vcrsa. Fn tho 

 form(M- caso its t(Mnp('i-;itnri\ i. o. its mc^ltinu' point will bo 

 sitnat(Ml a fow thonsandths of a. oonti^rado hijihor, and tho 

 volnmo o\' tho ioo in tho oahirimotor will movo downwards 

 ou tlu» iM-ancb o\' tlu> furvi» in tho attiMn])t^ to o-ain tho tom- 

 poratur(> of tho surronmUnji modinm. '.['hon tho indox will 

 movo slowly barkwards, in Iho otbiM- caso tho ooordinato of 

 spot'ilic volnnu> iA' tho ir(^ will movi^ npwards on »tho slopinu' 

 brancb, and \\\o indox of tho soalo-tubo will march forward, 

 1 think \\o i'onld diminisli Ihis inoonvonionco by lilhn^ tho 

 sonipnlously cloansiMl caloiamotor witb ri^pcatodly distillod 

 wattM' and by conlinim:, tlu> boilinj;- oporation to tho loasti i>os- 

 sibb> timo. 



In stn<iyinL;, tho pbonomona oi' tho movomont of .ulaciors, 

 wo of oonrso mnst ackn^nvlodiio tho }n>worful aotion of jiros- 

 tfuro, but wo will do woll ab'-!0 to boar in mind, thal an inoroaso 

 of pressuro, oqual to tho woi^bt oi' a vortioal oolumn of ioo 

 of 400 feet, is ro(purod oidy in order to mako tho nudtina; 



' still T rannot dispnlo tlio iH>ssil)ilily of llie hyiKithosis uphold l>y iny 

 fonwtM' fitnipanion, ProlVssor "NMlson, viz. that tho contraotion of tho glass 

 ro.^orvoir inav havo .-^oniolhins:' to »lo wilh tlioso variations. 



