68 REPORT— 1902. 



The results of a series of observations on the heat required to raise a 

 gramme of water from 0° C. to 100° C. were published by Reynolds and 

 Moorby in 1897. The quantity necessary is proved to be 418-4 joules. 

 Thus the mean heat required to raise a gramme 1° C. for temperatures 

 between 0° and 100' is 4*184 joules. This number is not far from the 

 4'2 joules adopted in 1896 as the number of heat units in a calorie. 

 Accordingly the suggestion has been made that it would be convenient 

 to change the definition of a calorie and take it to be one-hundredth part 

 of the heat required to raise one gramme of water from 0^ C to 100° C. 

 In this case, according to the mean number adopted by Griffiths (see 

 table), one calorie would be equal to 4-1854 joules, while according to 

 Reynolds and Moorby it would be 4-184 joules, while the degree centi- 

 grade through which it would be necessary to raise one gramme of water 

 in order to absorb an amount of heat equal to one calorie would be from 

 17° to 18° C. 



If this view were taken, then instead of Proposition II. of 1896 we 

 should read : — 



One calorie is the amount of heat required to raise the temperature of 

 a gramme of water from 17° C. to 18° C. on the scale of the hydrogen 

 thermometer, and is equal to 4-184 joules. 



It should be noted, however, that the Committee have not as yet taken 

 any resolution on the point, and that formally the propositions accepted 

 in 1896 and reprinted above are those which they have approved. 



It should also be mentioned that in deference to international repre- 

 sentations the use of the word ' therm ' was withdrawn in 1896, the name 

 being replaced by the word ' calorie.' 



Compel rinr/ and Beducinrj Magnetic Observations. — Report of the 

 Committee., conaisting of Professor W. G. Adams (Chnmnati), Dr., 

 C. Chree (Secretarj/), Lord Kelvin, Professor G. Chrvstal, Pro- 

 fessor A. Schuster, Captain E. W. Creak, the Astronomer 

 EoYAL, Mr. William Ellis, and Sir A. W. Rucker. 



The Committee have been in existence since 188.5, and have exerted a 

 beneficial and important influence on terrestial magnetism. Questions 

 connected with the comparison and reduction of magnetic observations do 

 not now, however, seem naturally to come under the cognisance of the 

 Committee. Of late years the reports have really been papers, for which 

 individual members have been responsible, and which have called for no 

 corporate action. The creation of an international committee naturally 

 affords a more direct means of communication between the observers 

 of different countries, whilst the existence of the journal ' Terrestrial 

 Magnetism ' affords a means of reaching with greater certainty the 

 limited class really interested in the subject. Under these circum- 

 stances it seems best that the Committee should not ask for reappoint- 

 ment. 



