38 THE BEGINNINGS OF LIFE. 



with scientific teachings and the evolution hypothesis) 

 they could have originated in those far remote ages, 

 when what we call c Life ' first began to dawn upon the 

 still heated surface of the earth. Before organic mate- 

 rials of the ordinary kind could exist, organisms must 

 have been present to produce them. Organizable com- 

 pounds of a certain kind must nevertheless have pre- 

 ceded organisms. And just as chemists are now able 

 to build up a great number of so-called organic com- 

 pounds in their laboratories, so it seems almost certain 

 that some such mobile compounds may have been 

 evolved by the agency of natural forces alone acting 

 on the heated surface of the earth at a period anterior 

 to the advent of living things. That mere saline sub- 

 stances are capable of undergoing change and rearrange- 

 ments under the influence of physical forces is a well- 

 established fact which nobody denies, and of which 

 we have an admirable instance in the conversion of 

 ammonic cyanate into urea. It is also certain, as Prof. 

 Graham showed, that one and the same saline sub- 

 stance may exist with its molecules now in the crystal- 

 loid and now in the colloidal mode of aggregation 

 according to the different influences to which it has 

 been subjected or under which it has been produced. 

 This, for instance, is the case with silica, with the 

 sesquioxides of chromium and iron, and with other 

 mineral substances. Nay, more, the absence of any 

 natural barrier between the crystalloid and the colloidal 

 mode of aggregation may be still further seen by the 



