[ 1 «> ] 
III. On the Capacity for Heat of Water between the Freezing and Boiling-Points , 
together with a Determination of the Mechanical Equivalent of Ileat in 
Terms of the International Electrical Units.—Experiments by the Con¬ 
tinuous-Flow Method of Calorimetry , performed in the Macdonald Physical 
Laboratory of McGill University , Montreal. 
By Howard Turner Barnes, M.A.Sc., I). Sc., Joule Student. 
Communicated by Professor H. L. Callendar, F.P.S. 
Received June 15,—Read June 21, 1900. 
Section 
Table of Contents. 
1. Introduction. ...... 
2. General theory of the method of Continuous Calorimetry. 
3. Measurement of Fundamental Constants. 
a. Clark cell; b. Resistance; c. Thermometry; d. Time; e. Weight. 
4. Description of Apparatus and Method of making the Experiments. 
5. Experimental Proof of the Theory of the Method. 
6. Effect of Stream-Line Motion. 
7. Preliminary Measurements of the Mechanical Ecjuivalent. 
8. Determinations between 0 and 100 C. at different Temperatures. 
9. The Variation Curve of the Specific Heat of Water in its relation to the work of other 
observers. 
Page 
149 
152 
158 
203 
225 
234 
237 
238 
257 
Sec. 1.— Introduction. 
The unsatisfactory state of our knowledge of the Mechanical Equivalent of Heat and, 
inseparably connected therewith, of the capacity for heat of water, is the more 
surprising when we consider the large number of physicists who have devoted their 
attention to this subject during the century just closed. Since the remarkable 
pioneer experiments of Count Rumford, undertaken just 100 years ago, to determine 
the nature of heat, the subject has been advanced step by step by different investi¬ 
gators. Conspicuous among these we may mention Regnault, who gave us the first 
idea of the mode of the variation of the specific heat of water with temperature, 
without, however, giving us any knowledge of the mechanical equivalent of heat ; 
Joule, who gave us the first measurements of the mechanical equivalent without 
attempting to study the thermal unit at different temperatures; Rowland, who by 
the remarkable accuracy of his experiments gave us not only a direct determination 
(314.) 13.8.02 
