332 ON PHYSICAL DATA 



ascertain, by all the means we have at our 

 command, the degree of this property, and what 

 are the circumstances which regulate its action 

 and preserve its continuance. 



Thus we find that a rigid body is held together 

 by means of attractive forces, which act upon 

 matter imperceptibly, their effects only become 

 apparent to our senses ; — that these secret forces 

 do act upon matter, and in many cases with con- 

 siderable power, we know from the circumstance 

 of applying an opposite force, in order to cancel 

 their effects. 



The next enquiry is, respecting this property 

 of attractive forces, to find the amount of them, 

 under every variety of circumstance, that gives 

 to material bodies their rigidity; which greatly 

 facilitates the translation of matter from one 

 place to another. If we extend our enquiries 

 we may combine the particular amounts of force, 

 which is required to disengage rigidity, in such a 

 manner as to elicit from them the laws which 

 govern their action during the time from whence 

 rigidity commences, to the time of attaining 

 its maximum action, and then again, to the 

 time when rigidity ceases. To prosecute our 



