102 Mr WhewelPs Address to the British Association 



It may be added — as a further reason why no observer should 

 be content without arranging his observations, in whatever part 

 of Physics, and without endeavouring at least to classify and 

 connect them — that when this is not done at first it will most 

 likely never be done. The circumstances of the observation 

 can hardly ever be properly understood or interpreted by others ; 

 the suggestions which the observations themselves supply, for 

 change of plan or details, cannot in any other way be properly 

 appreciated and acted on. And even the mere multitude of 

 analyzed observations may drive future students of the subject 

 into a despair of rendering them useful. Among the other de- 

 siderata in Astronomy which Professor Airy mentions, he ob- 

 serves ". Bradley ■'s observations of stars'" made in 1750 " were 

 nearly useless till Bessel undertook to reduce them in 1818."' 

 " In like manner, Bradley "'s and Maskelyne's observations of the 

 Sun are still nearly useless," and they and many more must con- 

 tinue so till they are reduced. This could not have happened 

 if they had been reduced and compared with theory at the 

 time ; and it cannot but grieve us to see so much skill, labour 

 and zeal thus wasted. The perpetual reference or attempt to 

 refer observations, however numerous, to the most probable 

 known rules can alone obviate similar evils. 



It may appear to many, that by thus recommending theory, 

 we incur the danger of encouraging theoretical speculations to 

 the detriment of observation. To do this would be indeed to 

 render an ill service to science : but we conceive that our pur- 

 pose cannot so far be misunderstood. Without here attempting 

 any nice or technical distinctions between theory and hypothe- 

 sis, it may be sufficient to observe that all deductions from theo- 

 ry for any other purpose than that of comparison with observa- 

 tion^ are frivolous and useless exercises of ingenuity, so far as 

 the interest of physical science are concerned. Speculators, if 

 of active and inventive minds, will form theories whether we 

 wish it or no. These theories may be useful or may be other- 

 wise — we have examples of both results. If the theories merely 

 stimulate the examination of facts, and are modified as and when 

 the facts suggest modification, they may be erroneous, but they 

 will still be beneficial : — they may die, but they will not have 

 lived in vain. If, on the other hand, our theory be supposed to 



