Chemistry and Physics. 221 
Exposing the two surfaces in turn to the radiation of a metallic 
blackened box heated by steam, and waiting until the es 
eter needle came to rest, the ratio of the deviations gave the 
e leaf. 
iL Velocity of Magnetization.—M. Deprez, in pursning othe re- 
searches on electro-magnets and their application to the registration 
pices: the iaffacn nce of t e tal of the cack 
measure the duration of the ar he used the method indivated 
in his communication on electric chronographs. The noe 
portion of the elecro-ma agnets consisted of cores two mms. in diam- 
eter and thirteen mms. in leneth. e coils contained fourteen 
fi au 
tried were the ordinary iron of commerce, the soft iron used 
specially for telegraphs, peer cast iron, cast see cretched 
and chilled, and gray cast iro e results were quite unex- 
pected, for all but the last kind of i ir on gave nearly the cae 
period ‘for magnetization and demagnetization. The first of these 
Was about -0015, and the second "00025. The gray cast vein ph 
transmissi 
signals can be obtained ‘at aera of aio ae seco nd, or with 
signals at regular intervals much greater pipet 3 is ‘titaahie 
— ony of cast iron appears to depend on its molecular 
emagnetization, the time of fall of the vt the magetintion, 
and the return of = style to its initial position. These a 
pata ie the num a only one cell is employed ; ge in- 
reasing the paca he rapidity of — = also increased. — 
Comptes Rendus, xxx, 1358; Phil. Mag., | BE. ©. 
