DR. IRVlTtt's EXi'ERtMENt. 5j 



There does not feem to me any difficulty ^n explaining fatis- 



fadorijy liovv experiments on the capacities of ice and water 



fnay be conducted without being expofed to the objeftions 



above ftated; at the tame time, tliough thefe experiments may 



be conclufive as far as they go, I have not been accuftomed -~but may not 



to confider them as altogether fo decifive of all arguments upon ^^^^"^"^Ptio'i- 



this fubje<5t. 



In a general way tben the experiments of Dr. Irvine Were Account of t)r* 



condnaed in the following manner. The capacity of water Y'""^'' "^='^^"* 

 . ** r • I • °^ experiment- 



being taken at unity, pains were u fed to afcertain the capaci- ing. 



tii6s of rnei'cary, river fand, pounded glafs, and iron filings, The capacities 



\\'ilh refpea to water, and confequently id each dthe^ in (he jf^J^^'^^J^^* ^ 



ordinary manner* It is at prefent of no importance what pro- giafs and iroa 



poitional quantities of the materials were employed, X his ^''"S^ ^^''.^ 



being done, the capacity of one or thele lubftances was ex- refpea to water* 



perimentally compared with that of pounded ice or fnow. — 



Every precaution was ufed to enfure fuccefs. The weight One of thefc 



and capacity of the vefTel was determined, and the colder and ^ing/againft 



hotter body alternately added to the other. The temperature pounded ice at a 



of the air was alwavs below 32, as was that of all the mate- J^'^P^''^^^''^ ^^ 



^ ' the place always 



rials and of the veflel. No water could therefore be formed, under 32"*. 

 In his firft experiments I believe Dr. Irvine ufed mercury, bat 

 afterwards I know that he preferred iron filings and fand. For 

 example, if the velTel and room were at 11^, let half an Example, 

 ounce of powdered ice from didilled water, at temperature 

 30® be poured on four ounces of iron filings at 11°, let the 

 temperature of the mixture be noted after ftining, the due al- 

 lowances made for the heat gamed by the velFel and the air, 

 and a proper calculation made. Let this experiment be re- 

 verfed by cooling the ice to 11°, and poiiring the iron filings 

 at 30° upon it, and let a calculation from this be compared 

 with the former and corrected by it. Finally, let thefe ex- 

 periments be compared with others where different quantities 

 of materials are ufed, and of ditferent temperatures, and you 

 have a view of the method employed for determining this point 

 by Dr. Irvirte, which does not appear to be obje6lionable upon 

 other grounds than all experiments for afcertaining capacities 

 are, nx>ne of which have any pretenfions to perfedl accuracy, 

 Dr. Irvine was far from being fatisfied that his experiments 

 VN'ere mathematically precHe. But he uniformly found the ca- 

 pacity of ice to be lefs than that of water, and that in a greater 

 rSitio than. is generally allowed, 

 . * E2 With 



