BIOLOGY: E. HUNTINGTON 
127 
TEMPERATURE OPTIMA FOR HUMAN ENERGY 
By Ellsworth Huntington 
MILTON. MASSACHUSETTS 
Communicated by W. M. Davis, December 26, 1916 
As a step toward the more exact determination of climatic optima 
for human species I have made a study of temperature in relation 
to (1) the death-rate, (2) the amount of work done by piece workers 
in factories, and (3) the strength of individuals as measured by the dyna- 
mometer. Although the matter is still in its early stages, the results 
show that the field of investigation is marvelously rich, and that only 
the surface has yet been scratched. 
(1) The death-rate is an excellent means of determining climatic 
optima. In most parts of the United States two maxima of deaths 
occur under widely different climatic conditions, one in winter and one 
in summer. Between the maxima come two minima both of which 
appear to be associated with essentially the same climatic conditions 
whether they occur in spring or fall. At first sight this may not be 
obvious since in the northeastern United States one minimum generally 
comes in June when the mean temperature is 65° to 70°F and the other 
in October when the temperature is 10° or 15° lower. Conditions of 
health, however, obviously lag behind the climatic conditions with 
which they are connected. An interval must elapse between the time 
when people fall sick and the time when they die. If allowance is made 
for this, the true optima would be found in May and September, two 
months which have about the same temperature. 
Since it is difficult to determine the exact amount of lag between 
given climatic conditions and the death-rate which they determine 
another method may be employed for determining the optimum tempera- 
ture. The months may be arranged according to their temperature 
without regard to the seasons of the year. If the figures thus obtained 
are smoothed, a lag in one direction is neutralized by a lag in the other. 
The method is illustrated in table 1. 
A glance at the last column shows that deaths in New York are numer- 
ous at low temperatures. They decline quite steadily until an optimum 
is reached when the mean outside temperature is about 65° F. Then 
they increase once more. The true optimum, however, is a trifle lower 
than 65°. Many people leave New York in summer and some of them 
die, but these deaths do not appear in the city records. Consequently 
the recorded deaths in July and August and to a less degree in Septem- 
ber and June are below the number actually occurring in the city's 
