94 SIMPLE NON-METALLIC COMBUSTIBLES HYDROGEN 



zinc is acted upon by dilute sulphuric acid, its properties with 

 respect to combustion were experimentally examined. The 

 history of its discovery by Mayow, Hales, and Cavendish, 

 in succession, was related. Being the lightest substance with 

 which we are acquainted, it was compared with the metal Pla- 

 tinum, as being the heaviest, bulk for bulk, of all bodies yet 

 known ; 100 cubic inches of hydrogen gas weighing about 2 

 grains avoirdupois ; while the same bulk of platinum weighs 

 544,34-3 grains, or about seventy-seven pounds and three-quar- 

 ters ; so that platinum is 242,000 times as heavy as hydrogen. 

 This naturally led to the subject of aerostation, which was 

 briefly treated of, so far as hydrogen gas is concerned ; a small 

 balloon, filled with it, being allowed to ascend from the lec- 

 ture-table. 



The discovery of the constitution of water, as a compound 

 of hydrogen and oxygen, was then traced, as successively 

 made out by Macquer, Watt (the improver of the Steam- 

 engine), Cavendish, and Lavoisier, and experimentally illus- 

 trated. And in exhibiting the composition of water by means 

 of a diagram, the Theory of Volumes in Chemistry was no- 

 ticed, in showing this fluid to be a combination of 1 hydro- 

 gen and 8 oxygen, by weighty but of 2 hydrogen and 1 oxygen 

 by volume or bulk. 



In commencing the history of SULPHUR or Brimstone, its 

 existence in the earth in an uncombined state was first no- 

 ticed, among the products of volcanos, in immense layers in 

 rocks of porphyry, and also, occasionally, in some of the 

 Superior or more recent strata composing the earth's crust. 

 Its existence in combination with copper, lead, iron, and 

 other metals was mentioned. Specimens of it were then ex- 

 hibited, some of them native, or as occurring in the earth ; 

 and its more obvious properties and characters were explained. 

 The effects of heat, in successively fusing it, changing its co- 

 lour and consistency, and rapidly converting it into vapour, 

 accordingly as the temperature is raised, were noticed. The 

 advantage taken of its volatility by a moderate heat, in 

 order to separate it from the bodies with which it is mingled 

 in the earth, and further to purify it, was then mentioned, and 

 the production of what are called Jlowers of sulphur , (some- 

 times, improperly, Jlour of sulphur,) by this means, was cited, 

 as an example of the chemical process of sublimation, which 

 was performed before the classes ; and the result of its ope- 

 ration on some other bodies also exhibited. Its combination 

 with water (milk of sulphur), and its solutions in oil of tur- 

 pentine and in alcohol being noticed, the properties of sulphur 

 as a combustible were examined, its spontaneous inflammation 



