70 Scientific Intelligence. 
Draper’s sae on oe published in 1844. Mr, Schwendler’s 
lamp differs in no respect from that proposed by Dr. Draper. 
From his epaviiionts Mr. Schwendler sohaluiien, that to produce 
the unit of light equal to the light emitted by a standard candle, 
from 300 to 725 units of current were necessary according to the 
size of the platinum strip, while with the use of the carbon electric 
lamp only 10 units of current were necessary. He thereupon states 
= conviction that “from an engineering point of view, light by 
nee can scarcely be expected to compete wi ith light by 
disintegration” (electric arc). He believes that light by inean- 
descence is not much cheaper than light by combustion. No 
reference is made to the late results of Edison on platinum sub- 
mitted to sikcraicieg currents in a partial vacuum.— Phil. Mag., 
Nov., 1879, p. 393. KG 
8. Re eport on the Electric Light.—Mr. Louis Hepenegtees in a 
report on the expediency of lighting the railroad stations in India 
y means of the “eons light, gives the following fefalth of his 
measurements. A no al candle, six to the pound, and consum- 
ing 120 grains per pbuh: ieee in —— the unit of light, a 
work of from 610 to 1365 megerga per second. An electro- 
dynamic machine with not more than 0-1 Siemew 8 units resistance 
in the seinen only from 10 to 20 megerga; so that one electric 
light produce ed ae at one place in the civenity is 50 times cheaper 
than the candle. Division of the electric light, on the other hand, 
Mr. Schwendler finds to be uneconomical. A dynamo-electric 
machine with the greatest pone tide of divisions of the movable coil, 
ives the most constant current. The strength of the current in- 
creases at first quickly, then is proportional to the velocity of 
rotation, then increases more slowly. he electromotive force 
decreases with a constant velocity of rotation more quickly than 
the entire resistance increases, and the more quickly the smaller 
the interior resistance of the machine is. When _the external 
resistance is zero, tlhe electromotive force reaches its maximum. 
Oo 
in volts, 
J 28°31. 23°87 16°27 Wo 0-81 2572 1ST 3°02 FOL P56 
A good dynamo-electric machine should make 700 to 750 turns in @ 
minute and afford a current in electro-magnetic units expressed 
by the formula 
J=0' Ve 
n an open circuit, and R represents the pregrad ope r the outer 
resistance. > 20, the loss of work reaches 12 cent.—L. 
 esceare heey of report on Electric light. pee ie , Waterlow 
Sons. 
