B06 Notices respecting New Books. 



M. Lemstrom, however, has succeeded in showing, in a 

 series of very remarkable experiments, that a rotating cylin- 

 der is capable of producing a real although excessively feeble 

 electrodynamic action. On putting a pasteboard cylinder 

 filled with air in rapid motion round a cylinder of soft iron, he 

 found that the magnetic condition of the latter was modified 

 by the rotation. M. Lemstrom has demonstrated that the mo- 

 dification can hardly be attributed to any other cause than the 

 electrodynamic action of the pasteboard cylinder. He intends 

 to continue these researches so interesting and important, es- 

 pecially from the theoretic point of view. 



As is sufficiently apparent from the preceding considera- 

 tions, the theory above formulated for the phenomenena of 

 unipolar induction does not rest upon vague and arbitrary 

 assumptions respecting the properties of the magnet and the 

 galvanic current. Quite the contrary ; it is based exclusively 

 on their known properties, discovered by means of experiments 

 or of investigations of another kind. The theory is indepen- 

 dent of the admission of one or two electric fluids, and 

 gives results in complete accordance with experience and with 

 the requirements of the mechanical theory of heat. We 

 therefore believe we can affirm that it furnishes the only ad- 

 missible and true explanation of the phenomena of unipolar 

 induction, which, as we shall see in the following section, 

 play a most important part in nature. 



[To be continued.] 



XL I. Notices respecting New Books. 



Elements of Dynamic ; an Introduction to the Study of Motion and 

 Rest in Solid and Fluid Bodies. By W. K. Cliffoed, F.B.S., 

 late Fellow and Assistant Tutor of Trinity College, Cambridge ; 

 Professor of Applied Mathematics and Mechanics at University 

 College, London. Part I, Kinematic. London : Macmillan and 

 Co. 1878. (Crown 8vo, pp. 221). 



^HIS is the first part of a work the completion of which will be 

 -*■ looked forward to with great interest by all students of Ma- 

 thematical Physics. Its scope is sufficiently described by its name : 

 it is a treatise on Kinematics. Change of motion as it occurs in 

 nature is due to the mutual action of bodies on each other. It is, 

 however, possible to study and describe the motion of a system 

 without taking into account the conditions that arise from these 

 mutual actions. The theory of motion when thus treated is Rme- 



k = k. In this way the same result is arrived at as by assuming that the 



ratio between these constants is equal to °, but its deduction be- 



comes more simple. 



