334 H. Hennessy on the Distribution of Isothermal Lines, 
This equated to zero gives 208 
SIRS. igs, 
tang. 2 A E( 4 (6.) 
2 
2K} sinisin 2.4 + H(i) cos2-4} 
Also, : = 
If in (6) we substitute the values of (+) and sini reepasanay 
we shall find 4=7° 24’ nearly, cos 2.4 and sin2 4 will both 
Tae negative; the above value of tang 
,.gives therefore a maximum value to H, and consequently 
the parallel which receives the greatest amount of solar heat 
during the half year that the sun is at the same side of the 
equator, is the parallel which has the latitude 7° 2’. 
6. The results of these investigations become applicable to the 
two great continents of the eastern and western hemispheres) 
for as these are both completely surrounded by water, they may 
be considered as two immense islands. The distance from 
ocean of the greater part of their surfaces, diminishes so much 
the action on their general climate of the waters by which they 
are surrounded, that the influence of. difference of latitude be: 
comes as a general rule, predominant over all other causes, 
the centres of most of their isothermal lines are transp0! a 
far towards the pole, that many of these lines circumscribe 
ert axis, or lie in surfaces which cut that axis more 0! 
obliquely. ae 
In en loue of a continent, an elevated table-land of limited 
dimensions is circumstanced nearly in the same way a8 a2 ae 
for its edges are surrounded with air having a mean tempeMt 
nearly uniform, and different from that lying on 1s of conti 
We may therefore expect to find, even in the interior © — 
nents, closed isothermal lines, as well as in the interior 0 
islands. : “the fornis 
The disturbing action of general winds will modily 4 the tem 
of the isothermal lines, according to the frequency 20 ‘the is 
perature of these winds. The warm winds will cause , direc 
thermals to recede from the coast towards the intent Sy winds 
tion opposed to that from which they emanate; the | towards 
will, on the contrary, cause the isothermals to advance v cot 
positive, and therefore 
i pou 2 thes? : 
they blow; when cold, their tendency will be to appre” 
centres towards thé same points. If we compound 
cies with the effect of differences of lores we bape : 
resultant direction towards which the isothermat *"™ i thee — 
displaced from their concentric position by the action ofall q 
disturbing causes. 
