NATURAL PHILOSOPHY. 157 



Eerr Paalzow has been making experiments from which he con- 

 cludes that there is no relation between the conductibility for 

 heat and that for electricity. He has experimented on the fol- 

 lowing substances, and has found that they have the following 

 order in point of conductibility of heat and electricity: — Heat: 

 Mercury, water, sulphate of copper, sulphuric acid, sulphate of 

 zinc, solution of sea salt. Electricity ; Mercury, sulphuric acid, 

 solution of sea-salt, sulphate of zinc, sulphate of copper, water. 



THE GALVANIC BATTERY. 



Prof. G. W. Hough, in his recent report as Director of the 

 Dudley Observatory at Albany, N. Y., gives the conclusions ar- 

 rived at, after a series of experiments with galvanic batteries, as 

 follows : 1. In the sulphate ot copper battery (Daniells' form), the 

 principal cause of decline in the strength of the electric current 

 is due to tlie formation of the sulphate of zinc. 2. The quantity 

 of electricity flowing in the external circuit dej^ends on the spe- 

 cific gravity of the sulphate of zinc solution. 3. When the sul- 

 phate of zinc solution approaches saturation, polarization takes 

 pkice in the battery itself, and, although electric motive force re- 

 mains the same, the internal resistance may be increased more 

 than a hundred times. 4. The sulphate of zinc solution (or any 

 fluid about the zinc) is useful only as a conductor of electricity. 

 5. The copper, or negative metal, is useful only as a conductor; 

 since it can be replaced by any negative metal, even by zinc it- 

 self. 6. The internal resistance of the battery has been sepa- 

 rated into two parts, namely, that due to the porous cell and that 

 due to the liquids employed. The specific resistance of the liquids 

 was found to be 13 ; that for a small clay cell 17, and for a leather 

 cell 7 ; since the resistance of the leather cell is less than one- 

 half that of a clay cell, we have used it in the construction of bat- 

 teries, as the quantity of electricity is nearly doubled, without 

 any increase of the surface. For the negative metal, in place of 

 the copper heretofore employed, we have used sheet lead. The 

 investigations have enabled us to compute, witli great precision, 

 the length of time a battery will generate its normal quantity of 

 electricity, provided the amount of electricity flowing in the ex- 

 ternal circuit is known, and the cajDacity of the vessel holding the 

 sulphate of zinc solution is determined. The specific gravity of 

 the sulphate of zinc solution should not be-less than 15°, nor more 

 than 30=^ Baume. 



SOUNDS OF TELEGRAPH WIRES. 



As the cause of the sounds frequently heard to jDroceed from 

 the wires in the open air, it has been customary to accept the 

 wind, and its producing the soundings by direct vibration, simi- 

 lar to those of the iEoIian harp. A difi"erent view of it, however, 

 and one which will recommend itself perhaps more generally, 

 is given by a railroad ofiicer in the " Austrian Railway Gazette." 

 U 



