194 WATER. [Lesson xxix. 



mosphere. But if, in the most common state of 

 ihe atmosphere, the Water be heated to the tem- 

 perature of 21 2 F. it then boils, and is converted 

 into an elastic fluid, or AQUEOUS VAPOUKS, or 

 ST2AM, which occupies about 1 800 times thcspace 

 that Water does, and is an invisible fluid, lighter 

 than common air, as 10 to 12, according to Kir" 

 waiiy and as 10 to 14, according to Saussure. The 

 degree of heat necessary to make Water boil in an 

 open vessel is, however, variable, according to the 

 purity of the Water and the weight of the atmos- 

 phere. The requisite degree of heat is generally 

 between 205* and 214 of Fahrenheit's thermo- 

 meter. When the pressure of the air is removed, 

 Water will boil with 90 of h.eat. Water, when 

 confined in the strong metallic vessel, called Pa- 

 pin's Digester, may be heated so intensely as to dis- 

 solve most earths, and to fuse metallic bodies. 



Next to fire, Water is found to be the most pe- 

 netrative of all bodies, and the most difficult to be 

 confined. It will pass through leather, bladders, 

 and other substances which will confine air : it will 

 make its way gradually through wood ; and is 

 only retainable in glass and some metals. Nay, it 

 was found by experiment at Florence, that when 

 shut up in a spherical vessel of gold, which was 

 pressed with a great force, it made its way through 

 the pores of the gold. 



Water, by this penetrative quality alone, may 

 be inferred to enter the composition of all bodies, 

 vegetable, animal, fossil, and even mineral : with 

 this particular circumstance, that it is easily, and 



with 



