[ 69 ] 



VIII. On the 'Expavjlon of JVater during Cojigcldt'ion. Com- 

 municated in a Letter from Stephen Dickson, M.D» 

 to Dr. MiTCHILL *. 



I 



T Is wcil known that water, in the ad of freezing, e5{- 

 pands with confiderable force. By calculations inrtituted on 

 fome experiments of the Florentine academicians, this force 

 appears to be fo great, as, in a fpherule of water only one 

 inch in diameter, to be fupericr to a refinance of thirteen 

 tons and a half. 



Some ingenious experiments on this fubje£l were made, a 

 few years ago, in Quebec, during a very cold feafon, by 

 Major Williams. He expofcd to intenfe cold, water in- 

 clofed in an iron bomb-ihell : the fuze was expelled to a 

 confiderable diftance, and a cylinder of cryftallifed ice was 

 fliot forth from the aperture, which, by Dr. Hutton's cal- 

 culation f, in one inftance, amounted to upwards of an 

 eighteenth part of its original bulk. 



The philofopher who obferves that this is not the uniform 

 effort of fpecific particles mutually receding from one an- 

 other, fincc the fpecific gravity of ice is greater than that of 

 water, naturally inquires to what caufe it ii to be attributed. 

 None feems to have a greater appearance of verifimilitude 

 than the fuggeftion of Dr. Black; viz. that, in the moment 

 of the convcrfion of water into ice, the latent heat fet loofe 

 enters into the air contiguous to, or combined with, the 

 water, and expands it with fuch vehemence as to cffe6l the 

 divarication of the ice into irregular mafles, and the cx- 

 plofion of refifting bodies. This explanation is counte- 

 nanced by a minuter attention to the experiments to which 

 it is applied ; for we find that ordinary rain-water was em- 

 ployed, and even that the bomb-lliclls were but " nearly 

 filled." 



To put the inquiry, however, to a more rigid teft, I pro- 

 cured two exa6lly equal and fimilar cylinders of tiji, dofed 



• From the Amnicn MeJical Rrpofitmy, Vol. Iff. No. i. 

 t Tr»nfa£lions of the Royal Society of Edinburgh, \q\. II. 



at 



