Leslie on Meteorology. 179 
column immediately fell about two inches in both tubes. Pro- 
fessor Leslie objects to Mr. Hawksbee’s inference from this 
experiment, because the outlet tube seems to have been wider, 
than that by which the air was admitted. But this is exactly 
the condition of the atmosphere in high winds. At the place 
where the equilibrium is disturbed (whether by rarefaction of 
the air, as most people think, or by its precipitation into the ocean 
abyss, with Mr. Leslie) the motion will be quickest ; and it will 
progressively slacken in the more distant masses of air, from 
their increasing inertia, friction, &c. Hence, therefore, to re- 
present this phenomenon by experiment, we must allow the air 
ample room to expand itself as it advances in the tube. We 
have, however, no objection whatever to the Professor’s theory 
of the variation of the barometer, in supplement to the com- 
monly received effect of wind. It is obvious, says he, that a hori- 
zontal current of air, must from the globular form of the earth, continually 
deflect from its rectilineal course. But such a deflection being precisely of 
the same nature as a centrifugal force, must hence diminish the weight or 
pressure of the fluid. The only question is to examine the amount of that 
disturbing influence. Though it should appear quite‘inconsiderable in the 
interval of a short space, it may yet accumulate to a very notable quantity 
through the wide extent over which the same wind is known to travel..... 
In the space of 288 miles, this diminution (of atmospheric pressure) would 
consequently be the 300th part of the incumbent weight, that is, 1-10th 
of an inch, when the wind is flowing at the rate of one mile per 
minute, nearly a seaman’s gale. Surely this result is so incon- 
siderable, as to indicate that some more direct operation of 
wind must produce the depression of the mercurial columns. 
Mr. Leslie refers to the same principles of deflection of the 
horizontal current, the phenomena of eddies, whirlwinds, and 
tornadoes. But we confess that his reasoning here appears to 
us loose and gratuitous. Why not call up some of the con- 
densed air ‘‘ from the vasty deep?” a task full as easy as get- 
ting it down; and the whirling rapidity of its escape, would, at 
the same time, have accounted for the jet d’eau and vortex of 
a water-spout. 
Under the second section, entitled thermometer, we are pre- 
sented with a verbose and rather common-place account of this 
useful instrument, to which is attached in a note, a long 
formula for computing in general the size of the scale of the 
differential thermometer. We shall give a specimen of this 
over refinement on a subject, with which no person, we believe, 
will ever perplex himself. Let the diameters of the two balls be 
expressed in inches by a and J, the diameter of the bore of the tube being 
denoted by d, and the yon ofa centesimal degree by x....By reduction 
22 a3 
** 200 (dep dd) + dab 
We should like to know how the interior diameter of the 
balls is to be found with a precision adapted to this for- 
mula teeming with cubes and squares. Every practical man 
must regard this equation as mere mockery. 
Vou. XIV. N 
