Additional Notes. 483 



Inflammable, or Hydrogenous Air. p. 82. 



This air was obtained by Dr. Mayow, and afterwards by 

 Dr. Hales, from various substances, and had been known, 

 long before, in mines, under the name of the fire damp. 

 But Mr. Cavendish ought to be considered as its real dis- 

 coverer; since it was he who, about the year 1766, first 

 examined it, pointed out the difference between it and atmos- 

 pheric air, and ascertained die greatest number of its pro- 

 perties. It was found by M. Lavoisier to be twelve times 

 lighter than common air. Its non-respirable character was 

 more fully determined by Scheele, Fontana, and Davy. 

 The products resulting from the combination of hydro- 

 gen with the sulphuric, phosphoric, and carbonic acids, 

 were discovered and investigated principally by Scheele, 

 Bergman, Fourcroy, Vauquelin, Gengembre, Kir- 

 wan, and Volta. It was first called Hydrogen by the 

 French Academicians, because it enters into the composition 

 of water. 



Composition of Water, p. 82. 



Water was believed, by the ancients, to be one of the four 

 elements of which every other body is composed. The opi- 

 nion that it is a simple substance seems generally to have pre- 

 vailed until the year 1781, when Mr. Henry Cavendish, 

 of Great-Britain, discovered, by several experiments, that it 

 is a compound, and formed by the union of oxygen and hy- 

 drogen. In a few months afterwards, the conclusion of Mr. 

 Cavendish was confirmed by the experiments of M. La- 

 voisier, and others: insomuch that, during the last fifteen 

 or twenty years, the composition of water has been gene- 

 rally considered as one of the best established facts in che- 

 mistry. It has been decomposed and recomposed, and found 

 to consist of 85 parts, by weight, of oxygen, and 13 of hy- 

 drogen. 



I'his discovery soon began to change the principles of che- 

 mical science. By furnishing a satisfactory exj)lanation of 

 many phenomena which were formerly difficult of explana- 

 tion, if not wholly inexplicable, it has, perhaps, contributed 

 more than any other single discovery to promote the progress 

 pf this branch of philosophy. 



