336 Mr. Gr. H. Knibbs : Mathematical Analysis of 



surface-areas of the two bodies submitted to experiment, 

 but as the linear proportions (1*138 and 1*139), thus appa- 

 rently agreeing with Stefan's theory. So close an agree- 

 ment, however, must be regarded as quite fortuitous, and it 

 is questionable whether it should be relied on. Further, if 

 we subtract the loss of carbon (G'2 grms.) and water 

 (15*8 grms.) from the lungs (22*0 grms. in all), so as to get 

 the net loss through the skin, it does not sensibly alter the 

 result. 



5. Increase of Loss due to Wind, 



Professor Osborne's experiments disclose the relatively 

 large effect of wind readily enough. Taking out results 

 under sensibly similar conditions as to temperature and 

 dryness, we see that the effect is well marked, so much so 

 that any effective analysis of quantitative results without 

 measures of wind velocity is out of the question. 



Table III. 



Temp. C. 



189 



20-2 

 233 

 31-7 

 34-0 

 350 

 37-2 



Relative 

 dryness. 



Loss with 

 no wind. 



Temp. C. 



Relative 

 dryness. 



•371 



grammes. 

 62 



175 



•329 



•674 



79 



21-7 



•683 



•674 



72 



23-9 



•630 



•822 



157 



32-8 



•757 



•742 



230 



336 



•805 



■802 



275 



35-8 



•788 



•819 



254 



394 



■827 



Loss with. 



wind, 

 grammes. 



74 



98 



76 

 252 

 235 

 362* 

 323f 



Mean 28"6 



•701 



161-3 



292 



•688 



202-9 



* Strong breeze. 



Less breeze. 



Bearing in mind that evaporation by diffusion is slow, and 

 varies (apparently) as a linear element of the exposed surface, 

 we see that the data for any satisfactory solution must include 

 wind velocity, or rather velocity of air movement about the 

 body subjected to experiment. 



These quantities found above (viz. 161*3 and 202*9) repre- 

 sent the means in grammes per hour of the loss in a man 

 weighing 68 kilogrammes respectively in sensibly still air and 

 in a breeze, and they are in the ratio of 100 to 126. The 

 temperatures, viz. 28°'G and 29°*2, and relative dryness 0*701 

 and 0*688 are sensibly equal and do not account for the great 

 difference of loss. 



