286 



NATURE 



{Feb. 8, 1872 



versities, not knowing the meaning of these terms, might 

 find himself quite at sea in some of the questions. In- 



gretted ; for just as the philosophy of Francis Bacon 

 used to be called the " New Philosophy," so might the 

 Natural Philosophy developed in the treatise of Tait and 

 Thomson be called the " New Physics." The experi- 

 mental science of the future must be based, we conceive, 

 upon the system therein elaborated. 



We are glad to notice a very good account of Morin's 

 apparatus for demonstrating the laws of falling bodies 

 (p. 49), which does not appear in the 1868 edition. The 

 principle of this, it will be remembered, is to cause a falling 

 body to trace its own path upon a rotating cylinder. The 

 accompanying diagram (Figs, i, 2) needs no explanation. 

 The vanes are for the purpose of producing uniformity 

 of motion in the revolving cylinder ; the falling weight is 

 a mass of iron, P, furnished with a pencil, which presses 

 against the paper on the revolving cylinder. The curve 

 traced can be proved to be a parabola, and the paths 



deed we do not find much introduction of the terms of 

 the Thomsonian Physics, and this is surely to be re- 



FiG. 3, Fig. 4. 



traversed in the direction of the descent are shown to 

 vary directly as the squares of the lines in the direction 

 of rotation. 



Under the head of '' Endosmose of Gases " (p. 97) we 

 find no account of the cause of diffusion of gases, the 

 experiments of Graham, the determination of the relative 

 velocity of atoms by Clausius, and the explanation of 

 such facts as the rate of diffusion of hydrogen being four 

 times greater than that of oxygen. But it may be argued 

 that this rather belongs to Chemistry. 



We are glad to see that the law which relates to the 

 volume of gases under varying pressures is now called 

 after its true discoverer, " Boyle's Law," but the experi- 

 ment, demonstrating at once the incompressibility of 

 fluids and the porosity of dense bodies, is, as usual, attri- 

 buted to the members of the Accademia del Cimento, 

 while it was in reality proved twenty years earlier with 



