iVe'ight in Bodies on being melted or he ate J. ^6^ 



the furrounding atmofphere, would prefs upon the fcale down- 

 ward with the whole force of the difference. If a little more 

 than half a pint of air was cooled over the fcale to ths heat of 

 the ice and glafs containing it, that is, twenty degrees below 

 the freezing point, the difference, according to General Roy's 

 table, would have been the eighth part of a grain, which 

 was the weight acquired ; but the air within half an inch of 

 the glafs veffel being only one degree below the freezing pointy 

 I cannot conceive, that even an eighth part of a pint of air 

 could be cooled over the fcale to twenty degrees below the 

 freezing point; nor that the whole difference of the weight of 

 the air over the fcale could ever amount to the ^zd of a grain, 

 I have, however, contrived an apparatus which is executing, in 

 which this caufe of fallacy will be totally removed. I (hall, 

 therefore, reft at prefent the ftate of this part of the fubject ; 

 and leave it only proved, that water gains weight on being 

 fi'ozen. 



I am. Sec 



G. FORDYCE, 



