On the Evidence of Certain Phenomena, &c. 317 
originates the centrifugal and other modifymg influences of the grav- 
itating power, which must always operate upon the great oceans of 
fluid and aerial matter which rest upon the earth’s crust, producing, 
of necessity, those great currents to which we have alluded. 
I have long entertained this conviction, but do not remember to 
have seen this great physical influence recognised in any degree, in 
its application to this subject, except by Sir John F. W. Herschel, 
in the third chapter of his popular treatise on astronomy,* where, by 
the aid of this rotative influence, he has been able to give us the 
most imposing support of the received theory of winds which has 
ever appeared, and in which the connection of the trades with the 
returning westerly winds, is, with some exceptions, correctly devel- 
oped. Sir John, however, has erred, like his predecessors, in ascrib- 
ing mainly, if not primarily, to heat and rarefaction, those results 
which should have been ascribed solely to mechanical gravitation, as 
connected with the rotative and orbitual motion of the earth’s surface, 
the influence of which he but partially recognizes in connection with 
this and another subject of inquiry. I may also add, that, had this 
able philosopher been fully conversant with the facts which relate to 
the course and other phenomena of hurricanes, he would probably 
have withheld the hypothesis which he has given in a note appended 
to the chapter which I have alluded to, although one of the princi- 
pal suggestions in this note has, undoubtedly, a proper connection 
with the subject. 
As I can but seldom allow myself to enter upon the discussion of 
these matters, the preceding suggestions may be taken for what they 
are thought to be worth by those under whose notice they may 
chance to fall; but, to prevent being misunderstood, I freely admit 
that heat is often an exciting, as well as modifying cause of local 
winds, and other phenomena, and that it has an incidental or subor- 
dinate action (though not such as is usually assigned) in the organ- 
ization and development of storms, and that, in certain circum- 
stances, it influences the interpositions of the moving strata of the 
atmosphere. Its greatest direct influence is probably exhibited in 
what are called land and sea breezes, or in the diurnal modifications 
which are exhibited by regular and general winds. But, so far from 
being the great prime mover of the atmospheric currents, either in 
* Art. 179 to Art. 200. 
Bt ach A a Raa SEN 
