PHYSICS. rs2o 



megohms, a value very much higher thau that iu the cells, thus sug- 

 gesting the formation of selenides which act as conducting bodies. 

 {Phil Mag., August, 1885, V, xx, 178; Nature, June, July, 1885, xxxii, 

 167, 215; Am. J. ScL, October, 1885, III, xxx, 313.) 



The Clamond thermo-battery has been improved iu the details of its 

 constructiou and its efficiency increased. A model made up of one hun- 

 dred and twenty pairs gave an electro-motive force of 8 volts and had 

 an internal resistance of oulj' 3-2 ohms. Another battery, containing 

 sixty pairs, gave an electro motive force of 3-C volts and an internal re- 

 sistance of only 0'65 ohm. Both batteries consumed about the same 

 amount of gas, about 180 liters per hour. {Am. J. Sci., June, 1885, 111, 

 xxix, 195.) 



Kayser has given to the Berlin Physical Society an account of the 

 measurements he has made on an improved form of Noe thermo-elec- 

 tric generator, differing from the old one in the tact that the bars of the 

 bismuth alloy are now connected by strips of an alloy offering greater 

 resistance to heat than did the wires formerly used. The resistance at 

 the ordinary temperature was 0-9 Siemens unit and rose as the gas con- 

 sumption increased to about 1*2 s, u. when this consumption was 00'=- *". 

 per hour. The curve of electro-motive force formed a straight line. 

 As to the cost of generating electricity in this way, a current of one 

 ampere for an hour cost about one pfennig, whereas with the Bunsen 

 cell the cost is about three times as great. {Nature, January, 1885, xxxi, 

 308.) 



Voii Waltenhofen has observed that if an electric current from any 

 source whatever be passed through an ordinary thermo-electric ele- 

 ment, and then the element be put on a closed circuit, a current Avill be 

 obtained contrary in direction to the exciting current. This inverse 

 current results of course from the difference of temperature produced 

 by the current at the junctions in virtue of the Peltier effect. If, how- 

 ever, the ordinary thermo-electric element be replaced by a dissymetric 

 thermopile, like the Noe battery, it will be observed that, according to 

 the direction of the current sent into it, the intensity of the secondary 

 current will vary, but its direction will remain the same. It is therefore 

 independent of the direction of the charging current. ( Wied. Ann., xxi, 

 300 ; J. Phys., December, 1885, II, iv, 572.) 



3. Electrical Units and Measurements. 



Jamieson has presented a paper to the Society of Telegraph Engineers 

 and Electricians upon electrical definitions, nomenclature, and notation, 

 calling attention to the very considerable confusion of the electrical 

 vocabulary in consequence of the rapid progress of electrical science, a 

 variety of terms being used to express the same idea on the one han<l 

 :iiid on the otiier the same term being used in many different senses. 

 Me suggests how these natnes should be restricted, and gives a set of 

 symbols for them by which they should always be represented in for- 

 11. Mis. 15 40 



