C e 7 3 
IX. An Account of a Method of measuring the comparative In- 
tensities of the Light emitted by luminous Bodies . By Lieute- 
nant-General Sir Benjamin Thompson, Count of Rumforcl, 
F, R. S. In two Letters to Sir Joseph Banks, Bart. P. R . S . 
Read February 6 , 1 794. 
Letter I. 
DEAR SIR, 
About two years ago, being employed in making a number 
of experiments to determine, if possible, the most oeconomical 
method of lighting up a very large workhouse, or public ma- 
nufactory, which has been erected in the suburbs of this city 
under my directions, where the poor, old and young, and all 
industrious people who are in want of work, are employed in 
a great variety of different manufactures, a method occurred 
to me for measuring the relative quantities of light emitted 
by lamps of different constructions, candles, &c. which is very 
simple, and which I have reason to think perfectly accurate. 
I sent you a verbal account of this little invention about a year 
and a half ago, by Dr. Baader, who wrote to me that you 
seemed to be pleased with it ; but, as I think it very probable, 
that he might not have been able to give you a complete idea 
of the matter from memory, I have determined to send you a 
short account of it in writing, which, if you should think it 
worthy of that honour, you will be pleased to lay before the 
Royal Society. The method is shortly this : — 
K 2 
