232 CHAP. XXV. PHOTOSYNTHETIC STORAGE OF SOLAR ENERGY 



± half a degree, the loss by radiation being thereby reduced 

 to a minimum. This very small loss is, however, completely 

 eliminated by the adoption of the particular method which 

 has been described. A very high degree of accuracy is 

 thus attained in the measurement of the energy of the 

 incident radiation I and of the transmitted radiation T in 

 terms of calories. 



Determination of the Coefficients of Transmission 



and of Absorption 



The mass of water in the Calorimeter plus its water 

 equivalent is, as already stated, equal to 5 • 16 grms. If G be 

 the galvanometric deflection due to rise of temperature in 

 the Calorimeter under full radiation, and g that produced by 

 transmitted radiation under similar conditions, then since 



1 mm. deflection represents a rise of - ° C. the units of 



50 



heat H and h produced in the two cases are : 



H=5-i6x^ 

 50 



h = 5 • 16 X — 



The coefficient of transmission =tt = ^ • • • (1) 



„ absorption = 1— — =1 — -^ . (2) 



The energy absorbed by the plant may thus be found 

 from the calorimetric determination of H — h, in which every 

 precaution had been taken in securing the highest accuracy, 

 notably by the elimination of the loss by radiation from the 

 Calorimeter. The accuracy of the calorimetric measurement 

 may be tested by the independent and almost simultaneous 

 determination of the coefficients of transmission and of 

 absorption by the Radiometer. 



When the Calorimeter is out of the way, the full radia- 



