36G 
ME. E. H. GRIFFITHS ON THE VALUE OF 
I'his agrees within 1 in 2000 with our later determinations.^ 
1892.—The difficulties experienced in obtaining an altogether suitable room for the 
work compelled me to have a special building erected in which to cany on the 
investigation. 
The apparatus is so involved and complicated that it requires weeks to put it 
together and to get it into working order, and such spare time as I had in the early 
part of this year was devoted to these preparations. On previous occasions the 
constant day and night changes in temperature of the rooms in which experiments 
were conducted had been a cause of uncertainty ; for the numbers, obtained by using 
resistance boxes or Clark cells whose temperature is constantly changing, are always 
of doubtful accuracy. I therefore designed a regulator which, except in cases of 
severe frost or extreme heat, automatically maintained the room at a constant 
temperature. I found this arrangement so effective that I have, in the hope that it 
may be useful to others, given a short description of it in Appendix II. 
If I endeavoured to adequately describe how much I owe to the assistance of others 
during this investigation I should unduly increase the length of this introduction. I 
must, however, express my thanks to the Council of the Royal Society, to Lord 
Kelvin, Lord Eayleigb, Professor G. Darwin, Professor Hicks, Professor J. J. 
Thomson, Dr. Feuszner, Dr. Guillaume, Mr. Ci^LUENDAR, Mr. Vernon Harcourt, 
Mr. Heycock, Mr. Larmor, and Mr. Neville for the encouragement and assistance 
they have afforded me. More especially am I indebted to Mr. Glaze brook, not only 
for his advice and help, but for the careful and laborious comparison of my resistance 
box with the standards of the B.A. ; and also to Mr. Skinner for his repeated com¬ 
parison of my Clark cells with the Cavendish standards. My thanks are also due 
to Mr. A. IvATT, B.A., Christ’s College, Cambridge, for his assistance in the experi¬ 
mental work during 1887 and part of 1888. 
Nearly the whole of the apparatus (some of it of a novel and intricate character) 
was constructed by, or under the direction of,, Mr. F. Thomas, Jesus Lane, Cambridge. 
Had it not been for his unremitting attention and skill, the results of my investiga¬ 
tion would have been far from satisfactory. 
From 1888 onwards I was assisted by Mr. G. M. Clark, B.A., Sidney College, 
Cambridge, who has from the commencement of our joint work been indefatigable in 
his exertions. Our respective contributions are so intimately associated that I find it 
impossible to make the remainder of this communication in the first person, and 
although, by his own wish, his name does not appear on the title-page, it should, in 
justice, be regarded as a joint contribution. 
* The Clavk cells used as oui' standards of E.M.F. are those given in Table IX. of Messrs. GlazE- 
BROOK and Skinner’s paper, ‘ Phil. Trans.,’ A, 1892, p. 605. 
