352 REGULATION OF TEMPERATURE 



A man entirely clothed in a garment of a total surface (s) of 

 19 xlO 3 sq. cm., of a thickness (t) of 75 xlO~ 2 cm. and having a 

 difference of temperature (d) on the two sides of 10 C., loses 

 heat (Q) as shown by the following formula : 



_ c xs xd 



Q = calories per minute, 



t 



where c = coefficient of conductivity, 



c x s x d x 3600 x 24 

 i.e. Q = t x l()oo calories per day. 



If the garment were of wool, c =68 xlO~ 6 , we have 

 _68 x!9 x36 x24 xlO~ 6 xlO 3 x!0 2 x!0 



75 xlO~ 2 xlO 3 

 = 1888-3 calories per day. 



The coefficient of utility of clothing materials may be determined 

 by covering with them a number of similar copper spheres filled 

 with warm water and finding how long they take to cool through 

 10 C. If the time taken to cool 10 C. by an unclothed sphere 

 with an external temperature of 12 C. be taken as 0, and the 

 time necessary for the same sphere (clothed) to cool to the same 

 extent be /, then t/6 = U (Coefficient of utility). 



TABLE LXIII. (FROM BERGONI^:). 



The efficiency of clothing depends in great measure on the j 

 arrangement of the fibres of the cloth so as to enmesh air and thus 

 form a stationary layer between the body surface and the outer j 

 air. The following table (Table LXIV.) from Lefevre gives an "| 

 idea of the protective value of clothing. His subjects were placed 

 in a rectangular box through which a measured amount of air was 

 passed. The temperature of the air just before it reached the 

 body and immediately after leaving the body was taken. If M, 



