Distrihutim Heat over the Globe. S71 
The deviations round the mean, that is, the inequality of the 
winters on the same isothermal line, increase in proportion as the 
annual heat diminishes, from Algiers to Holland, and from Flo- 
rida to Pennsylvania. The winters of the curve of BS'' are not 
found upon that of 51°, and the winters of 51° are not met with 
on the curve of 42°. In considering separately what may be 
called the same system (^climate.) for example, the European 
Region, the Transatlantic Region, or that of Eastern Asia, the 
limits of the variations become still more narrow. Wherever in 
Europe, in 40° of longitude the mean temperature rises 
In tracing isothermal lines between the parallels of Rome - 
and Petersburg, the coldest winter presented by one of these lines 
is not found again on the preceding line. In this part of the 
globe, those places whose annual temperature is 54° 5, have not 
a winter below 82°, which is already felt upon the isothermal 
line of 50°. If, in place of stopping at the most rigorous winter 
which each curve presents, we trace the lines equal winter 
temperature, (or the Isocheimal lines,) these lines, instead of co- 
inciding with the lines of equal annual heat, oscillate round 
them. As the Isocheimal lines unite points placed on different 
isothermal lines, we may examine to what distance their sum- 
mits extend. In considering always the same system of climates, 
for example, the European region, we shall find that the lines 
of equal winter cut isothermal lines, which are 9° distant. In 
Belgium (in latitude 52°, and in isothermal latitude 51° 8,) 
and even in Scotland, (in latitude 57°, and isothermal latitude 
45° 5,) the winters are more mild than at Milan, (in latitude 
* Throughout all Holland, 90 days of winter have a mean temperature of from 
36°.7 to 38°.7. At Milan, at Padua, and at Verona, the same season is only from 
34<°'7 to 3G°.7. The observations made in Belgium and Holland, offer also a 
very remarkable example of an equal quantity of heat distributed in the space of a 
year over a vast extent of territory. The mean temperatures scarcely vary from 
Paris to Franccker, over 3<| degrees of latitude, which, in the interior of a continent, 
should produce a difference of 3^ degrees of annual temperature. The canal of the 
Channel op.ens towards the nortli. The west winds blow, therefore, over a great 
