18 POPULAR SCIENCE. 



Some of us are old enough to remember the time when wash- 

 ing-soda was not so common and so cheap as now when 

 pearl-ash was habitually used for washing and other domestic 

 purposes, for which washing-soda is now universal. Well 

 might washing-soda be dearer than it now is, seeing that the 

 whole of this useful substance was got by a tedious process 

 out of the ashes either of actual sea-weeds, or from the ashes 

 of certain plants that grow on the sea-coast. At length a 

 chemist bethought himself that the sea the ocean held 

 illimitable quantities of the material of washing-soda, only it 

 chanced to be in the form of common salt. The proposition, 

 then, was to convert salt into washing-soda. A chemical pro- 

 cess suitable to the occasion was soon devised ; and now almost 

 all the soda that enters into commerce is made from sea-salt 

 either taken from the ocean or from salt-mines. 



When Mr. Woods, an assay-master in Jamaica, discovered 

 amongst his gold a metal that caused him much trouble, and 

 to which the name of * platinum' is now given, he little knew 

 that it was destined to work a revolution in the whole range 

 of chemical manufactures. Thus indeed it was to be, and in 

 this way : Few chemical manufactures can be efficiently car- 

 ried on without the aid of oil of vitriol, directly or indirectly ; 

 and before the discovery of platinum, every drop of oil of 

 vitriol had to be distilled from vessels of glass. The danger, 

 the labour, the expense of this may easily be imagined. Pla- 

 tinum retorts have made the case easy. Oil of vitriol can now 

 be bought at considerably less than a penny the pound. To 

 specify a tithe of the manufacturing utilities of oil of vitriol 

 would fill a volume. Amongst other applications, we are not 

 to forget its use in agriculture. Most artificial manures in- 

 volve the use of oil of vitriol in one way or another. When 

 the reader is informed that mummy bones are exported from 

 Egypt to be half dissolved in oil of vitriol, and in this con- 

 dition applied to English land, he may come to realise the 

 curious connection between a precious metal, the bones of 



