July 11, 1902.] 



SCIENCE. 



63 



suggesting modifications and substitutions 

 which will give the students some work for in- 

 vestigation in place of continuous verification. 

 The greater part of the descriptive sections 

 of the ' Practical Zoology ' is from the pen of 

 the late T. Jefl^rey Parker, and we note all the 

 characteristics which made his ' Elementary 

 Biology ' so popular. It is an interesting and 

 excellent book; and, in the reviewer's opinion, 

 a better single volume offering a year's course 

 in general zoology has not yet appeared. 



M. A. BiGELOW. 



Teachers College, 

 CoLtniBiA University. 



SOCIETIES AND ACADEMIES. 



NEW YORK ACADEMY OF SCIENCES. 

 SECTION OF ASTRONOMY, PHYSICS AND CHEMISTEY. 



At the May meeting of the Section, Professor 

 E. W. Wood, of the Johns Hopkins University, 

 read a very interesting paper on ' Anomalous 

 Dispersion and its Bearing on Astrophysical 

 Problems,' making special reference to the ex- 

 planation of the flash spectrum in this way. 



Dr. William S. Day, Columbia University, 

 read a paper on ' An Experiment Eelating to 

 the Application of Lagrange's Equations of 

 Motion to Electric Currents.' 



The experiment described was analogous to 

 one mentioned by Maxwell in his * Treatise on 

 Electricity and Magnetism,' Section 574, Vol- 

 ume II. Maxwell's experiment was made for 

 the purpose of discovering whether or not in 

 the expression for the kinetic energy of an 

 electric current there was a term depending 

 on the product of the current and the velocity 

 of the conductor. In a single linear circuit 

 having only one degree of mechanical freedom, 

 the expression for the kinetic energy of the 

 system in the most general case would be of 

 the form 



in which i is the velocity of the mechanical 

 coordinate, y is the current, / is a quantity of 

 the nature of mass, L is the self-induction of 

 the circuit, and E is the coefficient of the term 

 consisting of products. Just what mechanical 

 coordinate is to be represented by x is partly 

 a matter of choice. Maxwell chose one whose 



velocity means a motion of the wire in the di- 

 rection of its length. There is one other co- 

 ordinate which seems to be geometrically pos- 

 sible, although it is not one that is naturally 

 suggested by the most satisfactory hypotheses 

 now in vogue as to the nature of an electric 

 current. This other coordinate is one such 

 that its velocity means a rotation of the wire 

 carrying the current around its axis of figure. 

 If X has this meaning, then if the coefficient 

 K is not zero, Lagrange's equations of motion 

 show that if a current is suddenly started or 

 stopped in a wire there would be an impulsive 

 torque acting on the wire. The experiment 

 was performed to look for such an effect if it 

 existed. A straight piece of aluminium wire 

 30 cm. long and 0.25 cm. in diameter was sus- 

 pended by a quartz fiber in such a way that it 

 was free to rotate, and by means of merciiry 

 cups a current could be passed through it at 

 pleasure. No effect of the kind considered was 

 detected. If the value of K expressed in 

 C.G.S. electromagnetic units, and referred to a 

 centimeter length of the wire, had been as 

 great as 0.00002, it could have been detected. 

 S. A. Mitchell. 



SCIENTIFIC JOURNALS AND ARTICLES. 



The May number (Vol. VIII., No. 8) of the 

 Bulletin of the American Mathematical So- 

 ciety contains the following articles : ' The 

 March Meeting of the Chicago Section,' by 

 T. F. Holgate ; ' Concerning Angles and the 

 Angular Determination of Planes in 4-Space,' 

 by C. J. Keyser ; ' Note on the Sufficient Con- 

 ditions for an Analytic Function,' by D.E.Our- 

 tiss ; review of Scheffers's ' Theory of Surfaces,' 

 by J. M. Page ; review of ' Eecent Books on 

 Mechanics,' by E. B. Wilson; 'The Galois 

 Theory in Burnside and Panton's Theory of 

 Equations,' by B. S.Easton;' Shorter Notices'; 

 'Notes'; 'New Publications.' The June num- 

 ber (Vol. VIIL, No. 9) contains : ' The April 

 Meeting of the American Mathematical So- 

 ciety,' by F. N. Cole ; ' The Infinitesimal Gen- 

 erators of Parameter Groups,' by T. J. I'a. 

 Bromwich;'On the Parabolas (or Paraboloids) 

 through the Points Common to two Conies 

 (or Quadrics),' by T. J. I'a. Bromwich; 'A 

 Second Definition of a Group,' by E. V. Hun- 



