Notices respecting New Boohs. 229 



condescended to give some examples illustrating his general state- 

 ments. He revels in abstract generalities. It is very hard on the 

 poor reader to dose him with these undiluted generalities, a little 

 dilution with concrete cases would have made the dose much more 

 palatable. His devotion to generalities is so great that he skips 

 along in such a hurry when concrete questions arise that one can 

 hardly see the sequence of his remarks. Take, for example, his 

 description of Eriction, § 14, and what seems to be intended for 

 an explanation of its existence, but which neglects to explain how 

 it is an irreversible action, although described as a purely mecha- 

 nical effect due to the roughness of the surfaces. ".... if two 

 bodies, A and B. be pressed together, their surfaces of contact will 

 sink into one another, and if we attempt to move one body over 

 the other we shall experience a resistance in addition to the ex- 

 ternal forces." This statement about a force in addition to the 

 external forces is in itself quite unintelligible, but it evidently 

 omits to explain why a body is not just as much helped forward by 

 running down into the roughnesses as it is stopped by having to 

 be pushed up again out of them. Again, liquids are not rough, and 

 yet there is what comes to the same as friction between their parts, 

 and any really serious investigation of these questions should go 

 much deeper than Mr. Parker does, or else should at least w 7 arn 

 the student that the matter was not at all fully gone into. The 

 author evidently despises the concrete. How else can he write 

 that the latent heat of ice is " 79-25 calories or 3,292,052,964 

 ergs " ? Or, again, " 41,539,759*8 ergs or about 3 foot-pounds " ? 

 Such a degree of accuracy should include the specific heat of the 

 ether present, which Mr. Parker somehow ignores. 



Similarly, in proving the concrete fact that the internal energy 

 of a gas is independent of its density he gives the experiment 

 with two reservoirs, a very bad method, and does not there give 

 any reference to the very much more satisfactory porous-plug 

 method, though he himself gives this method further on. In this 

 same porous-plug experiment he does not condescend to give any 

 discussion of why the gas does not become warmed like other 

 bodies by friction. It is not because he is averse to investigating 

 things to the bottom that he slurs over these things. He tries to 

 get at general principles to explain everything. Take, for instance, 

 his treatment of capillarity. He is not content to do this in the 

 usual way. He is not content with the well-known method of 

 calculating the thermodynamic relations thereof. No, he must found 

 it directly on Carnot's theorem and the all-pervading friction. He 

 assumes that the vessel, capillary tube, liquid, and all are carried 

 sufficiently far down a mine or up a mountain for an observable 

 change in the length of the column of liquid raised to be caused 

 by the change in gravity. The tube must be given judicious taps, 

 and at last we are to be satisfied that all is right because " it is 

 obvious " that a certain expression must have a minimum value, when 



