558 SPECIAL METHODS OF DISCOVERY. 



the artificial formation of minerals, were made by this 

 method ; he passed feeble electric currents, during many 

 months, through water and other liquids containing 

 fragments of various stones, and by that means formed a 

 number of different crystalline minerals by electric ac- 

 tion. 1 The discovery of the partial conversion of wood 

 into coal by exposure to heat and pressure during several 

 years in a steam boiler, belongs to this method of research. 

 The experiments also of Sir William Thomson, of placing 

 small quantities of blue vitriol and other coloured soluble 

 substances in the bottom of very tall vertical glass tubes, 

 filled with water and hermetically sealed, in order to 

 ascertain the amounts of diffusion, &c., and other effects, 

 after a great length of time, are based upon this plan. It 

 is calculated that several hundreds of years will be re- 

 quired to complete the diffusive process. A whole mul- 

 titude of experiments of a similar kind might be easily 

 suggested, and the greatest difficulty in this, as well as in 

 all other methods of research, lies not in the suggestion of 

 new ideas, but in the large amounts of time, labour, and 

 expense necessary for testing them ; we require, in fact, 

 more just reward for the labour of original research, and 

 the experiments would be made. 



It was by employing widely different substances to 

 form the bob of a pendulum, and allowing the latter to 

 vibrate a sufficient period of time, that Bessel discovered 

 that the attraction of the earth had no specific relation to 

 different kinds of matter, but acted upon all of them 

 equally. The discovery of silver in the water of the 

 Pacific Ocean was a result of chemical analysis of the 

 metal sheathing of a ship which had been sailing during 

 several years in those waters, near the coast of South 

 America ; during the long-continued contact of the metal 

 1 See Noad, Manual of Electricity, 4th edit. p. 378. 



