15 
Dlsinhut'ion of Heat over the Globe. 
the increase of temperature from the pole to the equator, which 
is inequal under different meridians ; the distribution of the same 
quantity of heat over the different seasons, in the same isother- 
mal parallel, and under different latitudes ; the curve of perpe- 
tual snows, which is not a line of equal heat ; the temperature 
of the interior of the earth, which is a little greater towards the 
north, and in high mountains, than the mean temperature of 
the atmosphere under the same parallel ; and, lastly, the distri- 
bution of heat in the ocean, and the position of those bands, 
which may be called Bands of the warmest waters. As the 
limits of this extract will not permit me to enter, in a detailed 
manner, upon these different discussions, I shall confine myself 
solely to the principal results. 
It was formerly the custom to take the maximum and mini- 
mum of temperature observed in the course of a year, and to 
consider half the sum as the mean temperature of the whole 
year. This was done by Maraldi, De la Hire, Muschenbroek, 
Celsius, and even Mairan, when they wished to compare the 
very warm year of 1718 with the excessively cold years of 1709 
and 1740. De la Hire was struck with the identity between 
the uniform temperature of the caves of the Observatory of Pa- 
ris, and the mean of the observed annual extremes. He ap- 
pears to have been the first wiio had an idea of the mean quan- 
tity of heat which a point of the globe receives ; and he adds, 
‘‘ We may regard the air of the caves as the mean state of the 
climate Reaumur followed also the method of a maximum, 
though he confessed that it was incorrect f . He noticed the 
hours at which it was necessary to make observations ; and after 
1735, he published in the Memoirs of the Academy the ex- 
tremes of daily temperature : he even compared the produce of 
two harvests with the sum of the degrees of heat to which during 
two consecutive years the crops had been exposed. When he 
treated, however, of the mean temperature of the month, he 
contented himself, as Duhamel did thirty years afterw^ards, 
with recording three or four thermometrical extremes. In order 
to have some idea of the errors of this imperfect method, I may 
* Mem. de rAcad, 1719, p. 4. 
t M 1735, p. 559. 
