152 REPORT—1896. 
Replies were received from the following, and the Committee desire to 
thank those who so courteously responded to Mr. Griffiths’ inquiry for their 
very valuable assistance. 
Professor Ames, Baltimore. Professor Nichols, Ithaca, U.S.A. 
Professor Boltzmann, Vienna. Professor Olszewski (and Colleagues}, 
Professor Callendar, Montreal. Cracow. 
Dr. Chappuis, Bureau International, | Professor Ostwald, Leipzig. 
Sévres. Professor Paschen, Hanover. 
Professor Dieterici, Hanover. Professor Planck, Berlin. 
Professor Dorn, Halle. Professor Quincke, Heidelberg. 
Dr. Guillaume, Bureau International, Professor Remsen, Baltimore, U.S.A. 
Sévres. Professor Rowland, Baltimore, U.S.A. 
Professor Le Chatelier, School of Mines, Professor Runge, Hanover. 
Paris. Professor Stohmann, Leipzig. 
Professor Victor Meyer, Heidelberg. Professor Wiillner, Aachen. 
Professor Nernst, Gottingen. 
Extracts from such replies as contain definite suggestions bearing on 
the question of the unit of heat are printed in Appendix I. ; the letters 
have been translated, and those which merely give general approval to 
some such scheme as that outlined have not been included. No replies 
were received adverse to the suggéstion that an endeavour should be made 
to secure common agreement in the matter. 
The concluding propositions of Mr. Griffiths’ paper were substantially 
as follows : 
(I.) To adopt as the theoretical unit of heat a multiple (42 x 10°) of 
the erg. 
(II.) To adopt as the practical unit of heat, the heat required to raise 
1 gramme of water 1° C. of the nitrogen thermometer at some temperature 
t° C. as given by that thermometer. 
(III.) To adopt provisionally some formula expressing the specific heat 
of water in terms of the temperature over a range of, say, 10° C. 
If the number, 42 x 10° ergs, be adopted for the theoretical unit, then, 
according to the experiments of Rowland, the theoretical and the practical 
unit agree, provided that the temperature ¢° C. be 10° C, 
Mr. Griffiths, in the paper already referred to, has made a comparison 
of the results obtained by Joule, Rowland, Schuster, Micuiescu, and him- 
self, for the amount of energy required to raise 1 gramme of water 1° C. 
at various temperatures. The results differ according as the readings of 
Joule’s mercury thermometer are reduced to the scale of Rowland’s air 
thermometer, or to the scale of the nitrogen thermometer, as has been 
done by Schuster. 
In the first case the mean values are— 
At 10° C. (41-971+-023) x10®; and at 15° C. (41:°891+:023) x 106 ; 
and in the second — 
At 10° C, (41:958-029) x 108 ; and at 15° C. (41°875+-029) x 108. 
Tables of the values of the specific heat of water between 10° C. 
and 20° C. have been calculated by Mr. Griffiths, and are given in 
Appendix IT. 
The Committee have made an analysis of those replies which contain 
definite suggestions. 
