BY JAMES TOLSON, ESQ. 55 
ture, and an amount of heat is produced proportional to the carbon 
and hydrogen consumed. According to M. Dumas, an ordinary 
man burns per hour a quantity of carbon and hydrogen 
equivalent to .o2z2lb of carbon, and the heat developed will be 
12,906 X .022—284 units per hour. The heat thus developed 
serves to keep up the temperature of the body. If there were no 
means to prevent its accumulation the temperature would rise without 
limit, but such means are provided, and are so nicely adjusted 
that the body is maintained uniformly at g8° under all circum- 
stances. The surplus heat is carried off—tst, by radiation to cold 
walls or other surrounding objects ; 2nd, by contact of cold air; 
and 3rd, by perspiration, in which the fluids of the body are 
vapourised and heat becomes latent. With moderate temperature 
all three of these means are in operation, and only then is perfect 
comfort experienced. - In extreme cold perspiration is nearly 
suppressed and all the heat is carried off by radiation and con- 
tact of cold air. When the temperature becomes moderate, 
tnsensible perspiration ensues and the skin becomes moist. As the 
temperature rises the amount vapourised becomes progressively 
greater, and when air and walls have attained the temperature of 
the body, or 98°, the loss of heat by radiation and contact of air is 
suppressed, and the whole of the animal heat has to be carried off 
by perspiration, which then becomes excessive and takes the 
form of sweating.’’—Box, op. cit. 
TRANSMISSION OF Heat anp Laws or Cooitinc.—‘ The cooling 
of heated bodies may be effected in three ways—(1) By radiation, 
(2) by contact of cold air, and (3) by conduction. Putting U for 
the total loss from all causes, and & A and C, for the respective 
losses by radiation, contact of cold air, and conduction we have 
UVU= R+A + C.’—Box, op. cit. 
RADIATION.—At an early stage in the history of radiant 
heat, the following question arose :—A hot body, we all 
know, radiates heat towards those bodies which are of a 
lower temperature than itself, but does z¢ also radiate when 
surrounded by bodies of a temperature equal to its own, or 
of ahigher temperature ? In other words, is the radiation of 
a given body at a given temperature dependent upon those 
bodies which surround it, or is it independent of them ? 
Nearly a century ago Professor Prevost, of Geneva, 
propounded the latter theory, and since that time it has 
been gaining ground as the one most consistent with all 
observations. It has been developed by many eminent 
