HYPOTHESES. 23 



are probably a thousand more which are equally pos- 

 sible, but which, for want of anything analogous in 

 our experience, our minds are unfitted to conceive. 

 But it seems to be thought that an hypothesis of the 

 sort in question is entitled to a more favourable recep- 

 tion, if besides accounting for all the facts previously 

 known, it has led to the anticipation and prediction of 

 others which experience afterwards verified ; as the 

 undulatory theory of light led to the prediction, sub- 

 sequently realized by experiment, that two luminous 

 rays might meet each other in such a manner as to 

 produce darkness. Such predictions and their fulfil- 

 ment are, indeed, well calculated to strike the igno- 

 rant vulgar, whose faith in science rests solely upon 

 similar coincidences between its prophecies and what 

 comes to pass. But it is strange that any consider- 

 able stress should be laid upon such a coincidence by 

 scientific thinkers. If the laws of the propagation of 

 light accord with those of the vibrations of an elastic 

 fluid in as many respects as is necessary to make the 

 hypothesis a plausible explanation of all or most of 

 the phenomena known at the time, it is nothing 

 strange that they should accord with each other in one 

 respect more. Though twenty such coincidences 

 should occur, they would not prove the reality of the 

 undulatory ether ; it would not follow that the phe- 

 nomena of light were results of the laws of elastic 

 fluids, but at most that they are governed by laws in 

 some measure analogous to these ; which, we may 

 observe, is already certain, from the fact that the 

 hypothesis in question could be for a moment tenable. 

 There are many such harmonies running through the 

 laws of phenomena in other respects radically distinct. 

 The remarkable resemblance between the laws of light 

 and many of the laws of heat (while others are as 



