280 Mr. Herapatk on the Causes, Laws, and principal [April, 



minated. Nor, perhaps, is there any thing that could have 

 induced me to perplex myself any more with this subject ; but 

 the resolution I had formed to examine it thoroughly, and a fond- 

 ness for the plausibiHty of my preconceived notions that I could 

 not shake off, and which would oftentimes, even against my 

 inclination, prompt me to try to explain away the absurdity I 

 had brought out. The first thing that suggested itself for this 

 purpose was, that elasticity might spring from a different source 

 to what was commonly believed, and might be the property of 

 hardness ; for I observed that the harder the bodies are, gene- 

 rally speaking, the more elastic they are. Thus glass is very 

 hard, and likewise very elastic ; and the same is true of steel, 

 and most of the other metals. Upon this hypothesis, therefore, 

 I now tried to investigate the laws of gaseous bodies ; and as 

 far as I then carried my speculations, the conclusions I drew 

 exactly coincided with phaenomena. But reflecting more deeply 

 on the subject, I convinced myself that, however well these 

 inferences and phaenomena might agree, elasticity could not be a 

 property of hardness ; and, therefore, that the hypothesis I had 

 assumed could not be correct. At length, after a great deal of 

 intense and fruitless thought, I remembered that when, some 

 years before, reading the vulgar doctrine of the collision of hard 

 bodies, I was very far from being satisfied with it ; but looking 

 upon it then as an abstract and almost useless subject, I could 

 not summon resolution enough to give it a critical investigation* 

 Being now, however, drawn to the point by my analytical 

 inquiries, the recollection of this dissatisfaction excited me to 

 consider the circumstances connected with it attentively. The 

 result of this consideration was a theory for the collision of hard 

 bodies, so very different from the received theory, that it was 

 not until I had examined it in a variety of shapes, had brought 

 it to the test of experiment by my mathematical investigation 

 of the laws of gaseous bodies, and had found that a theory 

 something like it had been formerly given by Wren and Huy- 

 gens, that I could satisfy myself I had not committed some 

 oversight. But having considered and reconsidered it many 

 different ways, without discovering any thing that could militate 

 against it, 1 proceeded to carry on my theory as far as I judged 

 it would be wanted, and then assumed the following postulata as 

 the basis of my future inquiries. 



I Postulata. 



1. Let it be granted that matter is composed of inert, massy, 

 perfectly hard, indestructible atoms, incapable of receiving any 

 change or impression in their original figure and nature. 



2. Let it be granted that all solid and fluid bodies have their 

 smaller parts composed of these atoms, which may be of different 

 sizes and figures, and variously associated, according to the 

 manner which the constitution and nature of the bodies require. 



