MOVING FORCE. 
61 
tvasled In pxamining old facts under new appearances. Such 
disappointments have sometimes served indeed rather to 
stimulate than to damp their zeal fur making fartlier discoveries. 
But if a good theory in physical science be understood to com- 
prehend a distinct arrangement of what is known on the 
subject j or if it furnish the means of applying the experience 
of one case so as to determine the result of another of the 
same kind, but different in degree, or under different circum- 
stances ; it c.annot be questioned that snch information must 
tend to shorten the labours, and smootli the patli of the ingenious 
inventor ; and still more valuable must it be to those whose ta^k 
* • 
it is to distinguish the curious from t!ie useful, 'and to carry 
into execution the real but not the fanciful improvements. 
Neither does it appear that Mr. Atwood is supported in his 
opinion, bv the history of useful discoveries in mechanics. If vxtdl<M m 
Huygens and Hooke had not been sc'entific ns well ,ts ingenious 
men, we ntight possibly have been stiil ignor.int of the proper- 
ties of the balance regulated by springs. If Smeaten had not 
availed himself of just theory, as well as experiment, we might 
still have had to learn the principles by which we must be 
guided in applying water to the best advantage as a moving 
power. If a clear and strong understanding, and a mind richly 
stored with scientific attainments, had not been combined with 
wonderful fertility of invention, in the justly celcbr.itsd 
improver of the steam-engine ; incalculable labour might still 
have been wasted in performing operations wliicli are now 
accomplishhd with as much ease and regularity as the gentle 
motions of a time-piece. 
But if it were even granted, that all tliese distinguished men fiiemy i= aisn 
might have attained their object without the aid of theory ; it ad •-i::.i;ecut. 
■must still be acknowledged, that to these who have to follow 
their steps, and to apply their inventions and improvements to 
various purposes, under v. rious circumstances, it must be of 
essential importance to be free from perplexity in the princi[)!es 
by which they must be governed ; and it is under this impres- 
sion that I have been induced to state to this society some of the 
d'tficujtie* which have occurred to myself, la common, I believe, 
with 
