THE BEGINNINGS OF LIFE. 45 



whose action we are most familiar is water. This 

 fluid dissolves a great variety of different substances. 

 And although the materials so dissolved lose the 

 characteristics which distinguished them as solid ag- 

 gregates — such as form, hardness, specific gravity, and 

 other physical qualities — the actual matter is still there, 

 in a state of molecular diffusion and with all its 

 chemical properties comparatively unaltered. It is 

 recoverable, also, in the form of a solid aggregate — 

 either by the dissipation of the water by means of 

 heat, or else by the use of reagents for which the 

 molecules of water have a stronger affinity. 



Many elementary substances and compounds that 

 cannot be made by the agency of heat to assume the 

 fluid form (as well as many which can be so reduced) 

 are dissolved by immersion in water. And just as in- 

 numerable variations are met with in the behaviour 

 of different simple and compound substances under the 

 influence of a given degree of heat, so innumerable 

 variations exist in the behaviour of different substances 

 when brought into contact with water of a given tem- 

 perature. Some are very soluble, some less soluble, and 

 others quite insoluble j these differences being depen- 

 dent upon the different properties of the molecules of 

 the substances in relation to those of water. A union, 

 which can only be termed chemical, takes place between 

 the molecules of the substance dissolved and that of its 

 sol vent 1; though where these molecules are complex, 



* Speaking of the force which determines solution, Mr. Sorby says, 



