DISCOVERY BY EXAMINING THE INFLUENCE OF TIME. 559 



with the water, the former had extracted from the latter an 

 extremely minute proportion of silver which it contained. 



This method is often extremely valuable in enabling 

 us to discover minute residuary phenomena ; and those are 

 often the most important. The most influential pheno- 

 mena are not the most violent, but those which operate in 

 the most universal and constant manner. Some of the 

 greatest truths respecting geological and astronomical 

 phenomena the age of the Earth, the gradual diffusion 

 and dissipation of energy, the stability of the solar sys- 

 tem, &c. can only be ascertained by comparison of data 

 obtained at periods the widest possible of intervals asunder. 

 The influence of time is seen on the grandest scale in 

 the phenomena of astronomy and geology ; here the expe- 

 riments are made for us, and continued not merely for a 

 few years, but during hundreds, thousands, and even mil- 

 lions of years. 



i. By investigating the effects of extreme degrees of 

 force on 'substances. By subjecting water and other 

 liquids to great pressure, Colladon, Sturm, Oersted, and 

 Eegnault discovered that liquids in general are slightly 

 compressible ; that water is thirteen and a half times 

 as compressible as mercury; also that liquids are per- 

 fectly elastic. By subjecting various gases to powerful 

 pressure and extreme cold, Davy, Faraday, Natterer, 

 Thilorier, and others, proved that vapours and gases 

 were the products of the influence of temperature upon 

 very volatile liquids and solids. In the year 1835, Thilo- 

 rier solidified carbonic anhydride by the intense cold of its 

 own evaporation. By employing great pressure, and an 

 elevated temperature, Cagnaird de la Tour made several 

 remarkable discoveries respecting liquids and vapours, 

 and Andrews subsequently discovered the continuity of 

 the liquid, vaporous, and gaseous states. By employing 



