ON LATENT HEAt. 45 



Thouv6neI. But although his work is greatly extended, it ^'^per»ments and 

 tieverthelefs is not yet complete, fince much remains to be canthaddes^ 

 done, particularly with refpetSl to the green matter; for it is 

 difficult to conceive how it Qiould have no a6lion on the animal 

 economy when adminiftered internally, fince, applied externally, 

 it produces a veficating eftb6l. This obje6lion which I have 

 made to the author, the importance of which he acknow- 

 ledges, will doubtlefs be one of the motives which will de- 

 termine him to renew his experiments to remove doubts, and 

 to (hew more clearly what is to be expefted from the employ- 

 ment of the different parts compofing an ingredient from 

 which medicine has received fuch great benefits. 



X. 



Experimental Determinatiom of the Latent Heat of Spermaceti ^ 

 Bees* Wax, Tin, Bifnmth, Lead, Zinc, and Sulphur, By 

 Mr, William Irvine. Communicated hy the Author. 



Bedford Street, Aug. 24, 1 804. 



It will fcarcely be denied that the difcovery of the exigence Dlfcovery of la- 

 of latent heat in all fluid and vaporous bodies, is one of the^"^^"^^'^ ^^' 

 moft curious and important hitherto developed in the progrefs 

 of chemical philofophy. The merit of firft invefligating this 

 fubjed is univerfally attributed to the celebrated Black. By 

 a few fimple and clear experiments he demonftrated, that, 

 before any portion of ice can become water, it muft receive 

 or abforb as much heat as would have raifed the temperature 

 of an equal quantity of water by 1 40''. By other experiments, 

 in fome of which Dr. Black was aflitied by my father and Mr. 

 Watt, it was proved in a manner equally fatisfadory, that 

 water cannot be converted into fteara unlefs it admit a quan- 

 tity of heat fufficient to have heated the water 8 or 900^. 

 Having proceeded fo far by experiment. Dr. Black made a 

 general inference, and extended his theory to all cafes of fufion 

 and vaporization whatever. 



The only other philofopher, as far as I know, who has Dr. fcyine*s ex- 

 attempted to determine the exadt quantity of the latent heat in amination of the 

 Other bodies befides water, was Dr. Irvine. Landriani made o^jhe" hol\el be- 



fome fitJes water. 



