178 Analysis of Scientific Books. 
a serious refutation of this shower of atmospheric air-drops, push- 
ing themselves down the watery abyss from five and a half miles 
beneath the surface to the very bottom. Nor shall we alarm 
their fears, for the respiration of posterity, when this ‘‘ unceasing 
operation” shall have smuggled the whole atmosphere into 
its submarine vaults. We shall merely congratulate old Ocean 
on the possession of this soft, elastic, and self-adjusting pillow. 
To complete this new Neptunian theory, Mr. Leslie should have 
shewn how when this pillow becomes over-stuffed, the sur- 
plus air could be squeezed out, as occasion required, through 
one of Pluto’s spiracles, to inflate the bellows of the Cyclops. 
Having thus settled, in preliminary research, the constitution 
of the atmosphere, the Professor next enters on his account of 
meteorological instruments. The ordinary observations (says he) 
are confined to the weight and temperature of the air. There are other 
data still wanted, to determine at any time, the actual condition of that 
medium. The dryness or humidity of the atmosphere, its brightness or 
degree of illumination, the different depth of the ccerulean hue of the sky, 
and the variable disposition to chill the surface of the earth by impressions 
of cold transmitted from the higher regions,—these objects of inquiry 
should be conjoined with others of a more practical tendency, depending 
immediately on the mutable state of the weather. Such are the attempts 
to measure the daily evaporation from the ground, to register the quantity 
of rain which falls, and to mark the direction and indicate the force or 
velocity of wind. A complete apparatus of meteorological instruments will 
therefore include primarily the burometer, thermometer, hygrometer, pho- 
tometer, @thrioscope, cyanometer ; and comprehend likewise the atmometer, 
rain-gauge, drosometer, and anemometer. We shall review this series in the 
order of enumeration*. 
In treating of the influence of dryness and moisture on the 
barometrical altitude, he says, ‘‘ but even supposing a column of 
air to become suddenly charged with humidity, before its sub- 
sequent dilatation had, by diffusing it produced an equilibrium, 
still the additional pressure would have been extremely small, 
not exceeding at a moderate computation the jifteenth part of 
a mercurial incht.” If Mr. Leslie will consult Mr. Daniell’s 
elaborate tables, inserted in the eighth volume of this Journal, 
he will find, that the pressure of the vapour in the atmosphere, 
amounts occasionally to 6-10ths ofa mercurial inch, or 9-15ths, 
and during the month of September, as there recorded, it was 
on an average, more than 5-10ths, though it was seldom 
thoroughly charged with moisture, to use the Professcr’s term. 
Most of our readers are probably acquainted with Mr. Hawks- 
bee’s ingenious experiment to illustrate the influence of wind in 
depressing the mercury in the barometer. Having connected 
the cisterns of two barometers with a horizontal tube, he then 
transmitted across the mercury in the basin of the one, a rapid 
current of air from a globe into which it had been previously 
injected to three or four times its usual density. ‘The mercurial 
* Pp. 397, + Lbid., col. 2. 
