2 ULTIMATE FACTS. THEORIES. [iNTROD. 



uncomplicated, incapable of further subdivision, and fundamental ; 

 and this we are contented to receive as an ultimate fact , the result 

 of a law in constant and universal operation. The accumulation 

 of observations and experiments affords us Experience ; points out 

 the ordinary succession of phenomena, and teaches us the ways of 

 Nature. If these phenomena are found to present a certain 

 uniformity, we are authorized to refer them to the operation of 

 one common Cause, and we are thus led to the expression of the 

 Law which regulates their occurrence. Proceeding in this way, we 

 are enabled to explain the whole train of phenomena which have 

 been investigated, that is, to devise a Theory which develops the 

 rationale of their occurrence. 



But sometimes our experiments and observations throw an 

 imperfect light upon the phenomena which are the subjects of 

 investigation ; or the latter are so remote, or so little under our 

 control, as to render both observation and experiment extremely 

 difficult, and, in some cases, impossible. The " instances " which 

 we are enabled to collect, are consequently dubious and ob- 

 scure, and point darkly, or not at all, to ultimate facts ; they 

 present little or no general resemblance, and cannot be properly 

 associated together. Here is no foundation on which to build a 

 theory : but great advantage may be gained, if, with the little light 

 we derive from these particular observations, aided by previous 

 knowledge of general laws, we can frame a hypothesis, offering 

 some explanation of the phenomena. The adoption of such an 

 hypothesis, even for a temporary purpose, will " afford us motives 

 for searching into analogies," may suggest new modes of observa- 

 tion and experiment, and " may serve as a scaffold for the erection 

 of general laws/' 



Previously to the time of Lavoisier, chemists were perfectly fami- 

 liar with the occurrence of combustion under various circumstances; 

 but the opinions (hypotheses) which prevailed as to the real nature 

 of this process, afforded a very unsatisfactory explanation of it. 

 Subsequently, however, by the labours of Lavoisier, Davy, and 

 others, this complex phenomenon has been observed in all its 

 phases ; it has been carefully analysed, and has been proved to 

 occur in all cases, where substances possessed of strong chemical 

 attractions, or different electrical relations, are brought within mu- 

 tual influence. The ultimate fact, thus arrived at, is, that intense 

 chemical combination always gives rise to the evolution of heat, 

 and, in many instances, to that of light also. 



Again, a great number of observations have shewn that bodies 



