141 
1879.] Ij. Schwendler —On a new Standard of Light. 
taken by Colonel Tennant and developed with pyrogallic acid. Some of 
the photographs taken in Calcutta with the same instrument on dry 
plates by Sapper Meins, who was sent out by the Secretary of State to 
take photographs of sun-spots, also showed the same structure. Owing to 
want of the proper appliances none of these photographs had been 
enlarged, and they were too small to give anything like such satisfactory 
results as those obtained by M. Janssen because the size of the disc was 
only 4 inches instead of 12 inches. 
The following papers were read r— 
1. On a neio Standard of Light.—By L. Schwendleb, Esq. 
(Abstract.) 
The author illustrated his paper by exhibiting an actual standard. 
The new standard of light consists of a piece of pure sheet platinum of an 
U shape, cut accurately to fixed dimensions. When a sufficiently stiong 
electric current is made to pass through the platinum, it becomes white- 
hot and emits a brilliant light. He showed experimentally how the 
intensity of this light could be varied, i. e., the magnitude of the standard 
altered,_by varying the current, and that when the current was kept 
constant, the light was rigorously constant also. 
Mr. Schwendler defines the new unit of light as : 
The quantity of light emitted from apiece of pure platinum iveighing 
(ce) grm. and having the most convenient shape and size, ivlien a constant 
current of (y) webers per second passes through it. 
The advantages of the new standard are : 
The Light is perfectly constant if the current is kept constant; it 
allows a correction to be made for the variation of the current when this 
variation is known ; it can be reproduced very accurately anywhere ; its 
magnitude can be altered to any extent to suit certain practical purposes 
by simply varying the elements of weight, shape and size of the plati¬ 
num, or the strength of the current passing through it; it does not alter 
of itself, either in intensity, size, or position, and therefore most accurate 
photometric measurements can be made with it; the standard can be easi¬ 
ly made to fit into any adopted system of absolute units. Hence the new 
standard fulfils all the recognised conditions of a perfect and rational stan¬ 
dard, and Mr. Schwendler therefore proposes it should be adopted in future 
in England and India in lieu of the Standard Candle. 
Mr. Schwendler concluded by saying that there would be no practical 
difficulties met with in the introduction of the new standard for technical 
purposes. Gas Companies and other Corporations that may in time 
be formed to supply that necessary commodity “ light,” to the goneral 
public would find it quite easy and highly satisfactory to themselves to 
