256 Chemistry. [Lecture 33. 



There were chemical experiments instituted at 

 the same time to account for the supposed gra- 

 dual diminution of the water of the sea. Van 

 Helmont hinted that water, by repeated distilla- 

 tion, might be converted wholly into earth. Mr. 

 Boyle repeated the distillation of the same water 

 fifty times in the clearest glass vessels, and ob- 

 tained at each distillation a quantity of earth. 

 He says, a friend of his obtained at least three- 

 fourths of an ounce of earth from one ounce of 

 water. Boerhaave suggested many doubts and 

 suspicions, and endeavoured to invalidate the 

 credit of these experiments. He says they were 

 not performed with accuracy, that water was en- 

 tirely a pure substance, but that it was capable of 

 being rendered impure by a variety of mixtures, 

 especially of air, which he says is a chaos ; so 

 that if any other bodies were found in water, it 

 was only accidental: hence he supposes, and 

 with justice, that the earth in these experiments 

 proceeded either from dust in the air contained 

 within the distilling vessels, or from some other 

 cause which introduced it previous to the expe- 

 riments. These experiments, therefore, only 

 serve to show the imperfection of all chemical 

 analysis. 



Though water cannot be regarded as a simple 

 elementary substance, yet there are not different 

 sorts of pure water ; for water obtained in any 

 manner whatever, either attracted from the air, 

 by deliquescent salts, or from salts themselves, 



