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IV. Fundamental Principles of Molecular Physics. Reply to 



Professor Bay ma. By Professor W. A. Norton. 



To the Editors of the Philosophical Magazine and Journal, 



GENTLEMENj 



THE paper by Professor Bayma, entitled "Fundamental 

 Principles of Molecular Physics/' published in recent 

 Numbers of the Philosophical Magazine, is obviously of a cha- 

 racter to demand some answer at my hands. In replying to it 

 I do not propose to take up in detail, and in the order in which 

 they occur, all the points made by the learned author, nor strive 

 to make good all the positions before taken in my reply to his cri- 

 ticisms on my ' Memoir on Molecular Physics/ My aim will 

 be to present the important points on which we are at issue in 

 what appears to me to be their true attitude, in such order as 

 may best conduce to a clear understanding of the whole subject, 

 alluding occasionally to such side issues as may demand atten- 

 tion. The cause of truth will apparently be best subserved in 

 this way ; and this is of far more importance than that my ac- 

 curacy and consistency should be formally justified by defend- 

 ing anew every position I have taken. Whether any important 

 position, either taken in my original paper or in my reply to 

 Professor Bayma' s criticisms, has been effectually assailed or 

 not, there will be a fair opportmrity of judging when the whole 

 ground shall have been gone over. 



By way of introduction to a general view of the case, I will 

 first remark that I did not mean to convey the idea, in what 

 Professor Bayma calls my first proposition, that molecular 

 science is "without established principles," is a "pure heap of 

 hypotheses.-" I had no thought of implying that I did not re- 

 gard the existence of matter, with, its fundamental properties of 

 inertia, &c, the operation of forces of attraction and repulsion 

 in nature, and other kindred principles, as established truths ; 

 and it is surprising that such an intimation should have been 

 thrown out by my critic, who, with all his unquestionable acute- 

 ness, is, I doubt not, animated by a sincere desire to deal justly 

 and with entire fairness. I meant, and could reasonably be 

 supposed to mean, no more than that every new theory of mole- 

 cular physics must of necessity involve one or more hypotheses 

 that " have been rendered more or less probable, either by in- 

 duction from observations or a priori reasonings," and to be 

 tested by a comparison of the deductions from the theory with 

 facts, and therefore that its foundation is essentially hypotheti- 

 cal — just as it is affirmed that the strength of a structure is the 

 strength of its weakest part. The doctrine is, in other words, 

 that a new theory of molecular physics must, when first pro- 



