some Experiments in Climatological Physiology. 341 



S. Thermodynamic Elements of the Formula. 

 The thermodynamic elements of the evaporation formula 

 depend upon the temperature and the dryness, relative 77 or 

 absolute J. The proper formula for the case of evaporation etc. 

 from the human body can be discovered only by experiment, 

 since the skin action (and the lesser losses of C0 2 and H 2 

 from the lungs) is by no means identical with evaporation 

 from a water-surface, owing to reactions of the peripheral 

 nervous system. It would no doubt be theoretically pre- 

 ferable and probably practically advantageous to use the 

 absolute temperature 2D sa y« Hence, using <£]_ and <p 2 for the 

 form of the functions for temperature and dryness, yet to be 

 determined, we have for E the evaporation or loss per unit 

 of time 1 



E = U€) .kfo){l + *[V + a(l-«-»*)]}W 5 (17) 

 [where n has the value indicated in 17 a], 

 or else — I 



E = ^(C) • ^ 2 (?){l + /.V-ZV 2 + mV 3 }W 2+e - wVC . (17 a) 

 See also (14), (15), (16). We can of course accept J£ as 

 T-r273°. Instead of £ or rj we might also use T-*. It 

 remains to deduce the form of the functions <f>i and 2 , and 

 probably it is better to use f than 77 for reasons hereinafter 

 indicated. 



9. Difficulties of Analysis. 

 The difficulty in arriving at secure deductions as to the 

 relative influence of increase of dryness or increase of tem- 

 perature arises from the large differences, due to unrecorded 

 factors affecting the results, as given by the observations 

 themselves. For example, we have : — 



Table IV. 



Observation 



No. 



Air 



Temperature. 



Eelative 

 Dryness. 



Absolute 

 Dryness in mm. 



Loss in 

 grammes. 



15 



22-5 C. 



•333 



674 



80 



17 



233 



•674 



1433 



72 



37 



37-0 



•814 



37-99 



270 



38 



37-2 



•819 



38-60 



254 



That is, there is a loss of 8 and of 16 grammes less, though 

 the conditions (so far as recorded) would lead one to 

 anticipate larger results. 



The clothing was the same for the first pair of results, 

 and practically the same for the second pair of results. 



Phil. Mag. S. 6. Vol. 24. No. 141. Sept. 1912. 2 A 



