Experipients on the Fufton of Ice. 34 j 



th^t in th« globe itfelf, remained alipofl: perfe£Hy at reft. He even found that he could 

 make the fluid in the upper part of the tube aflually boil, vyirhput that in the lower pare 

 of it appearing to the hand to be fenfibly warmed. This fact not only fervcd to (liew that 

 heat is propagated in fluids chiefly, if not altogether, by virtue of thefe motions which arife 

 from change of denfity, but alfo that this tranfportatlon cannot be cfFtclcd iu a do%vnwaid 

 direClion, 



It is an opinion generally received among philofophers, that water cannot be heated 'v-\ 

 contact with ice. Our author faw that this pofition muft; be in a great meafure true with 

 regard to watef uppa which, ice floats ; becaufe-thc hot water mud afcend and be cooled 

 by caufing part of the ice to meltf while the cold water from this laft would defcend to the 

 bottom, and tend to prefetve the uniformity of temperature. But he faw likewlfe tliat the 

 cafe would be very different if the ice were at the bottom. The inferences which this courfe 

 of argument would point out are fingular and ftriking, and they are not lefs fo for being 

 announced to us under the incontrovertible fanftion of experiment. Natural as the induc- 

 tion is, from the valuable experiments of Count Rumford, it ftiU feenis in fomc menfure 

 aflonilhing to aflert, that water may be adually made to boil, and kept in that ftate without 

 melting a piece of ice, plunged in it, with more rapidity than could be cfTcclLd by cold water 

 at 40 degrees. 



The direft: experiments with ice and hot water are related at large in the Eflay. A cir- 

 cular cake of ice, three Inches and an half thick, weighing lol ounces, and nearly as large 

 as the internal diameter of a cylindrical glafs jar, which w-as 4,7 inches (its height being 14. 

 inches), was gently put into the jar containing fix pounds i \ ounce troy of boiling-hot water. 

 It was entirely melted in two minutes and fifty-eight feconds. 



The fame experiment was "repeated; but Inftead of the ice being fulTered to fwim at the 

 furface, it was fattened down in the bottom of the jar, and the hot water poured upon it. 

 The ice was retained in the jar by means of two flcnder and elaflic pieces of deal about 

 i-8th of an Inch thick, and l-4th of an inch wide, which, being a very little longer tlian the 

 internal diameter of the jar, were of courfe flightly bended when they were introduced into 

 it horizontally; and on being put down to the ice at right angles to each other, thev con- 

 fined it from rifing to the furface when the water was added. A circular piece of (Irong 

 writing-paper was laid upon the ice to proteift it from the adion of the boiling-hot water 

 while poured, which" was aftefwartls removed, as gently as pofliblc, by means of a firing 

 faftened on one fide;"" and to prevcnnhe glafs jar from being cracked by the fudden appli- 

 cation of the boiling-hot water, a firiall quantity of cold water was firft poured in, to cover 

 the ice to the height of about a quarter of an inch. The hot water was poured againft 

 the middle of ftie circular piece of paper. 



The jar with the ice an<l the hot waTer in it being placed on a table near a window, the 

 paper which covered the furface of the ice was gently drawn away, and this Count prepared 

 himfcif to obferie at his eafe the refult of this moft interefting experiment. 



A very few raomcnts were fufhcient to flicw that his expeQation with regard to it would 

 not be difapjiointcd. In the former experiment a fimilar cake of ice had been entirely 

 ■melted in lefs than three minutes ; but in this, after more than twice that time had elapfcd, 

 the ice did no't flicw any apparent figns of beginning to meft. Its furface rciiiained fmooth 

 ai-.,) flihr'i", ^rd t1i<- v.-?.!fv iiirttttdiiteJj- in coiitaiJl With' it apjjcareif to be pcrfcdlj at red ; 

 . ■^•j.\\\q i'ui. 10 'jJ^'iii- •.',h r;. iif,.(j.n izii ?! ''-'■'■.ItniffrV 



