348 R.marhabU Cmchifion refftnlng the Melting of la. 



In the two laft experiments, as the circular tin plate which covered the furface of the ice 

 ferved to confine the thii\ fticct of water which was between the plate and the ice — as 

 this water could not rife upwards, being hindered by the plate — and as it had no tendency 

 to defcend— it is probjble that it remained in its place ; and as it was ice-cold, it was not 

 capable of melting the ice on which it repofed. But as the tin plate had a circular hole 

 in its centre, the furface of the ice in that part was of courfe naked ; and the ice-cold 

 water in contaft with it being difplaced by the warmer and heavier water from above, 

 an excavation in the form of a fliallow bafin was formed in the ice by tliis dcfcending 

 warm current. 



The warm water contained in this bafin overflowed its banks as foon as the bafin began 

 to be formed ; nnd iffliing out on that fide'which happened to be the lowell, opened itfelf 

 a pafljgc under the tin plate to the edge of the ice, over which it was precipitated, and fell 

 down to the bottom of the jar. The water of this rivulet being warm, it foon formed for 

 itfelf a deep channel in the ice ; and at the end of the experiment it was found to be every- 

 where deeper than the bottom of the bafin where it took its rife. 



This manner of accounting for the appearances in queftion feenied to the Count to be- 

 xjuite fatisfaQory ; and the more he meditated on the fubje£l, the more he was confirmed 

 in his fufpicions that all liquids muft neceflarily be perfect non-condudors of heat. 



On tliefe principles he was now enabled to account for the melting of the ice at the 

 bottom of the hot water, as alfo for the flownefs with which that procefs went on; and 

 encouraged by this fuccefs he proceeded with confidence to plan and to execute ftill 

 more decifive experiments ; from the refults of which he confiders the important fads in 

 queftion to4iave been put beyond all poflibility of doubt. 



If water be in fa.51 a perfeft non-condu£l:or of heat, that is to fay, if there be no commu- 

 nication whatever of heat between neighbouring particles or molecules of tliat fluid (which 

 is what he fuppofes) -, then, as heat cannot be propagated in it, but only in confequence of 

 the motions occafioned in the fluid by the changes in the fpecific gravity of thofe particles 

 which are occafioned by the changes of their temperature, it follows that heat cannot be 

 propagated downwards in water, as long as that fluid continues to be condenfed with coldj 

 and that it is only in that diretlion (downwards) that it can be propagated after the water 

 has arrived at that temperature where it begins to be expanded by cold; which has beea 

 found to be at about the 40th degree of Fahrenheit's fcale. 



Reafoning on thefe principles, he was led to this remarkable conclufion : namely, that 

 •water which is only eight degrees above the freezing point, or at the temperature of ^o degrees, niufl 

 be able to melt as tr.uch ice in any given time, -when Jianding on its furface, as an equal volume of 

 -water at any higher temperature, even though it -were boiling-hot. 



The experiments by which this unexpe£led refult was confirmed and eftabliflied muft be 

 deferred to the concluding part of this abftraft. 



ni. EsperU 



