Chemistry and Physies. 241 
of the plate and also by forming derived circuits between the 
en 
branches were confluent. This plate was then made to revolve 
about an axis perpendicular to the middle of the elliptical plate, 
and various ingenious arrangements were made to allow the 
terminals of the galvanometers and those of the battery to follow 
the motions of the plate. If the electrical current possessed in- 
“ertia, a difference of potentials would be created by the revolu- 
tion of the plate. This difference of ae: being formed at 
the extremities of the minor axis of the ellipse would cause a 
current in the galvanometer whose spelen were connected 
with the ends of this axis. The various errors incident to this 
method of experimenting were closely examined and the results 
of the experiment appeared to the writer to warrant the asser- 
tion that he could wager lind to 1 that no movement of the 
needle of the galvanometer greater than one of his scale divisions 
could be ascribed to the rh Dis of the electricity. His caleula- 
aie ee 
tion leads him to the formula p= ao in whieh ys is the kinetic 
@ 
energy of a current of the magnetic density of 1 in a cubic milli- 
meter of a silver neat Pp the difference of potential between 
the ends of the minor axis, @ the thickness of the metallic coating 
of the revolvin lite J the strength of the current passec 
through the plate, and w the angular velocity of sti plate. The 
value obtained for y¢ was j= 0°0000185 mm.” for o e seale divis- 
10n which ~ author selected. He is led to iuiave that the 
value of ; ld be much lar bad in Hs eer and that a positive 
result saat ai obtained wit em if the difficulties of experi- 
mentation could be overcome. suaaaihy der Physik und she re 
No. 12, 1881, pp. 581-591. 
13. Elécirisal Units reconamended by the Hlectrical CG, ane *€88 a 
1881.—(1.) The fundam tal units are the centimeter, the gram 
and the second (C. G.8.). (2.) The volt and the ohm retain the 
present value, viz: 10° and 10°. (3.) The resistance of one ohm 
one volt is PPh: an ape (6.) The quantity of clectvity 
afforded by one ampére in one second is called a coulomb. (7.) 
A farad is defined to be that capacity by which one coulomb in 
one farad gives a volt.—Ann. der Physik und Chemie, No. 12, 
1881, p. 708. 
14. Blemonca ‘y Lessons in Electricity and cy deta by S : 
VANUS P. THompson. 446 12mo. London, 1881 Macoliitan 
0.)—The beginner who wishes to make himself rie vega 
with the fundamental experiments of Electricity and Magnetis 
and with the principles which have been deduced from them, will 
