equivalent of silver has been made at the observatory of the Physical
Institute of Würzbourg, and the results are that an ampere current
flowing for a second, or a coulomb of electricity deposits 1.1183
milligrammes of silver or 0.3281 milligramme of copper, and decomposes
0.09328 milligramme of water, a result agreeing closely with that of
Lord Rayleigh recently communicated to the Physical Society. An ampere
therefore deposits 4.0259 grammes of silver per hour; Kohlrausch's
value is 4.0824, a value hitherto accepted universally. This value is
so useful in measuring electric currents with accuracy, and free from
the disturbances of magnetism, etc., that it is eminently satisfactory
to find the German value agree with that of Lord Rayleigh, which will
probably be adopted by English electricians.

* * * * *




A NEW STANDARD LIGHT.


Herr Hefner-Alteneck has suggested a new standard light for
photometric purposes, which promises to be very simple and effective
in operation. The light is produced by an open flame of amyl-acetate
burning from a wick of cotton fiber which fills a tube of German
silver 1 in. long and 316 mils. internal diameter; the external
diameter being 324 mils. The flame is 1.58 in. high from top to
bottom; and it should be lighted at least ten minutes before using the
light for testing. A cylindrical glass chimney surrounds it to ward
off air currents. About 2 per cent. of the light is absorbed by the