PHYSICS. 477 



the whole beiug 1.122. Testing a Latimer Clark standard cell by this 

 method, the author obtained for its value 1.434 volts. Hence the vari- 

 ation in the strength of the zinc sulphate solution aflects the electro- 

 motive force. {Am. J. ScL, November, 1884, III, Xxviii, 374.) 



Beetz has ju-oposed a simplified form of Daniell cell for use as a nor- 

 mal element, which is of remarkable constancy at different temperatures, 

 and which, owing to its high resistance, falls off only slightly on closed 

 circuit. The battery for charging the quadrants of an electrometer is 

 made by filling glass tubes, S*^™ long and 5'"™ in diameter, one-half full 

 of plaster of Paris mixed with solution of copper sulphate, and the other 

 half with plaster mixed with zinc sulphate solution, wires of copper 

 and of zinc being placed in the corresponding mixture, the external 

 ends being soldered together alternately. Twelve of these form a row, 

 and twelve of these rows form the battery, the difference of potential 

 of the 144 cells being 152 volts. The entire battery occupies a space 

 of only 16'''" square. {Wied. Ann., kxii, 402; Phil. Mag., September, 

 1884, V, XVIII, 173; Am. J. Sci., November, 1884, 111, xxviii, 390.) 



Another standard cell devised by Beetz is a modified Latimer Clark 

 cell. It consists of a tube in which a compressed cake of mercurous 

 and zinc sulphates is placed, the zinc being on one side of this cake 

 and the mercury on the other. The electro- motive force was 1.44 volts, 

 whicl) on short circuiting for 48 hours fell only to 1.408. Its resistance 

 is 15.7 ohms. {Nature, October, 1884, xxx, 568.) 



At the Montreal meeting of the British Association one of the sub- 

 jects for general discussion was the seat of the electro-motive forces of 

 (he voltaic cell. It was opened by O. J. Lodge, who inclined to the 

 chemical theory, in opposition to Sir William Thomson and others, who 

 favored the contact theory. Printed copies of notes prepared by Dr. 

 Lodge, containing the points involved in the question at issue, were 

 distributed before the meeting. {Nature, October, 1884, xxx, 594.) 



Quite a number of new forms of voltaic cell have been proposed. 

 Eeynier has studied the effect of varying the size of the elecirodes in a 

 battery upon its electro-motive force, and has constructed two cells 

 w^hich he calls maximum and minimum cells. The former has a copper 

 plate plicated so as to have a surface of 30 square decimeters, or 300 

 times as large as that of the zinc plate, which is simply a wire 3""" in 

 diameter. The containing vessel has a capacity of 800 c. c. and the 

 cell has a resistance of 0.2 to 4 ohms, according to the liquid used. 

 The latter, while exteriorly of the same size, contains a negative elec- 

 trode 5 sq. dm. in size, the positive being a copper wire 0.5™'" in diam- 

 eter, the surface immersed being 1 sq. cm. With these batteries he has 

 measured the maximum and minimum electro-motive force of the or- 

 dinary electrolytes. In dilute sulphuric acid, the zinc being amal- 

 gamated, the maximum electro- motive force observed was 1.072 volts 

 and the miuimum 0.272. The maximum cell, charged with a liquid 

 composed of 20 parts salt in 100 of water, he proposes as a standard 



