358 D.*s Reply to C.'s Observations [May, 



tion. Should this be the case, it must be considered that C. 

 does not work by the ordinary rules of philosophizing; and, 

 therefore, unless he employs some preferable means to sanction 

 his inductive asseverations, he must pardon common capacities 

 for distrusting a system so very comprehensive as to prove truth 

 error, wrong right, and, perhaps, even black white. 



Besides what 1 have shown, we have other equally happy 

 consequences flowing from C.'s physics that would be not a 

 little amusing if we had time to pursue them. Of these, I shall 

 merely select the following two or three, which will set C.'s 

 depth and knowledge of the subject in question in the most 

 advantageous point of view. C. says " that the intensity of the 

 stroke between two bodies moving towards opposite parts is 

 equal to the sum of their momenta ; " and, therefore, when one 

 of them is at rest before the stroke, the intensity must be equal 

 to the momentum of the other. These propositions precisely 

 coincide with Mr. Herapath's. Moreover, C. says that a hard 

 body striking a hard fixed plane perpendicularly acts with a 

 force equal to its momentum. This force is evidently the inten- 

 sity of the stroke. Hence, therefore, the momenta in both cases 

 being equal, the intensities of the strokes, and consequently the 

 effects of these intensities on the motions of the bodies are 

 equal. But C. tells us the one body after the stroke remains at 

 rest on the plane ; therefore, the other body striking the quies- 

 cent one likewise remains at rest after the stroke. Now, though 

 this agrees with Mr. H.'s theory, it is decidedly at variance with 

 the old. The old theory makes the two bodies after the stroke 

 to go on together; and hence the colHsion deprives the striking 

 body of only a part not of the ivhole of its motion. C. has con- 

 sequently embraced views in direct opposition to the theory he 

 means to advocate ; and that too in the very elementary parts of 

 it ; and what makes it better than all in the elementary part of 

 a subject, " whose principles," he tells us, " are as nearly as 

 possible self-evident." It is not, I think, in the power of C. or 

 any person whatever, to refute Mr. Herapath, or overturn the 

 theory of heat of our illustrious Newton. Let me remind C. that 

 it is of no avail to attempt to annihilate theories which have been 

 fairly deduced from facts, by mere assertions. Indeed I enter- 

 tain some doubt whether C clearly understands the theory 

 which he has undertaken to advocate. 



From the examples I have given, an estimate might easily be 

 made of the value of the rest of C.'s observations. I might 

 hence be very well excused from attending to his other remarks ; 

 but lest he should conceive I dismiss them too hastily, I will 

 accompany him a step or two further. 



Mr. Herapath, in his theory of coUision, says, " if a hard ball 

 or other hard body be held against a fixed hard body or plane, 

 and in this way receive the impulse of another body," the force 

 with which the one side of the intermediate body is driven towards 



