REPORT OF THE SECRETARY 115 



(8) At normal indoor temperature, in still air and with the subject 

 normally clothed and at rest, body heat losses are distributed as fol- 

 lows: 



Per cent 



Evaporation of water 24 



Radiation 46 



Convection 30 



(9) Tests with the thermoelement show that the air temperature 

 falls to room temperature very rapidly as the distance from the body 

 increases. That is, there is a steep temperature gradient in the first 

 centimeter or so from the body surface. With the thermoelement 30 

 cm. away no effect of the presence of the body could be detected. 



(10) The Abbot-Benedict work (Table A) indicates that the radi- 

 ation loss from a nude subject is about twice as great for a room tem- 

 perature of 15° as it is for a room temperature of 26°. This evidence 

 does not entirely support the " suit-of-clothes " theory referred to by 

 DuBois. In explanation of tliis theory, he says (p. 385, 1927 ed. Basal 

 Metabolism) : "A constriction of the peripheral blood vessels (oc- 

 curs) and the amount of heat carried to the surface is relatively small 

 in projDortion to the heat produced. * * * fpj^g patient really 

 changes his integument into a suit of clothes and withdraws the zone 

 where the blood is cooled from the skin to a level some distance below 

 the surface." 



(11) Normal fluctuations in humidity indoors produce negligible 

 effect upon the radiation loss. This is to be expected. Our bodies, 

 about 300° absolute, radiate almost wholly between the wave lengths 

 4/x, and 50/* with a maximum at lOfx. Water vapor absorption is so 

 strong for much of this range and so nearly negligible near the 

 maximum, that its possible effect is so fully produced, even by the 

 humidity of an ordinary room, that the effect of changes of the quan- 

 tity of water vapor in the ordinary room is small. Were the air of the 

 room exceedingly dry, changes might be noticeable. 



WORK IN THE FIELD 



(a) Solar radiation work at thi^ee desert mountain statioyis. — As 

 far as possible, daily measurements of the intensity of solar radia- 

 tion have been made at the Smithsonian stations at Table Mountain, 

 Calif., and Mount Montezuma, Chile. Also similar measurements 

 have gone on regularly at the cooperating station of the National 

 Geographic Society on Mount Brukkaros, South West Africa. 



Pending completion of the statistical investigations of the results 

 of the two last-named stations, as mentioned above, only the results 

 obtained at Mount Montezuma are being published at present. By 

 continued cooperation of the United States Weather Bureau, the daily 



