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287 



Washington, D. C; and on the 24t.h, at the High School Ob- 

 servatory of this city. 



The reference to a paper presented at the preceding meeting 

 of the Society, led Professor Henry to make some remarks on 

 the corpuscular hypothesis of the constitution of matter. 



He stated that this subject has occupied attention at every period 

 of the history of science; and though, at first sight, speculations of 

 this kind might appear to belong exclusively to the province of the 

 imagination, yet, in reality, he considered this hypothesis a iruitful 

 source of valuable additions to our knowledge of the actual pheno- 

 mena of the physical world. Though simple insulated facts may oc- 

 casionally be stumbled upon by a lucky accident, the discovery of a 

 series of facts, or of a general scientific principle, is, in almost ail 

 cases, the result of deductions from a rational antecedent hypothesis, 

 the product of the imagination ; founded, it is true, on a clear analogy 

 with modes of physical action, the truth of which have been esta- 

 blished by previous investigation. 



In constructing an hypothesis of the constitution of matter, the 

 simplest assumption, and indeed the only one founded on a proper 

 physical analogy, is, that the same laws of force and motion which 

 govern the phenomena of the action of matter in masses, pertains to 

 the minutest atoms of these masses. 



It is a well established fact, that portions of matter at a distance 

 tend to approach each other, and when they are brought very near, 

 to separate, and still nearer again, to approach; and so on through 

 several alternations. In the present state of science, we consider 

 these actions as ultimate facts, to which we give the name of attract- 

 ing and repelling forces; and without attempting to go behind them, 

 we may study their laws of variation as to intensity and direction 

 under different circumstances, and particularly in reference to a 

 change of distance. Bodies or masses of matter are also subjected 

 to fixed laws of motion, which have been classed under three heads, 

 namely, the law of inertia, or tendency to resist a change of state, 

 and to move in a straight line with a constant velocity; the law of 

 the coexistence of separate motions; and the law of the equahty of 

 action and reaction. 



The explanation of a mechanical phenomenon consists in its ana- 

 lysis, and the reference of its several parts to the foregoing laws of 

 force and motion ; and as no phenomenon, whether it relates to 

 masses or the minutest portions of matter, is fully explained until it 



VOL. IV. 2 P 



