infiance, vegetables, calcarious ftorie* 

 nitre, &c. That a fluid body may 

 become a folid, is nothing extraof -«■ 

 dinary ; we fee that water becomes 

 as folid as a ftone, and remains fo, 

 in a place fufficiently cold* There 

 are perhaps in the world no fub- 

 ftances which are by their nature 

 fluid : for all fubitances yet found 

 may be, by different operations, 

 principally by a fufflcient degree of 

 heat, rendered fluid ; and all fluids 

 may be changed into folid bodies 

 by applying to them a fufflcient 

 degree of cold. Mercury itfelf was 

 rendered as malleable as any other 

 metal, by Profeffor Brown at St. Pe- 

 tersburg, by a very great degree of 

 cold. 



Since that kind of air is known, 

 which goes now under the name 

 of fixed air, and which Van Hel- 



montj 



