NATURAL PHENOMENA ARE OMNIPRESENT. 23 



so extremely minute, that our senses, even when aided 

 by the most effectual appliances at present known, are 

 able to detect only a very small proportion of them. 

 Through want also of knowledge of the proper methods 

 of detecting them, as well as through want of investi- 

 gations made with the assistance of known methods, 

 whole multitudes of phenomena doubtless remain unknown. 

 We have reason to believe that every part of a mass of 

 liquid, and of a volume of gas of uniform temperature, is 

 continually diffusing into every other part ; but we have at 

 present little means of actually detecting it. The com- 

 plexity also of the phenomena of nature is generally so 

 great, that we are at present only able to completely 

 understand a few of the very simplest. From these and 

 many other circumstances we have great reason to believe 

 that we are still surrounded on every side by an immense 

 number of natural phenomena which we do not perceive, 

 or of the existence of which we have but little conception. 

 There are also very many things which do not at present 

 exist in nature, but which by processes of reasoning we 

 can show may exist, provided we can secure the proper 

 conditions. Amongst these we may fairly include a whole 

 multitude of substances belonging to homologous series of 

 organic bodies. 



If we may also in this case judge of the future from 

 our experience of the past, unexplored regions of science 

 lie in nearly all directions, and even some of the com- 

 monest phenomena probably remain still unknown. For 

 instance, the most abundant of all common substances, 

 oxygen, was not discovered until the year 1774 ; and the 

 gases in general, although several of them were common 

 enough, were not individually known and isolated until 

 comparatively recent times, evidently because scientific 

 knowledge had not sufficiently advanced to enable men 



