our (tor-)Mentor is mistaken in assuming a
uniform weight for the atmosphere. It differs in different places.
During our lecturing-tours, we have frequently observed an involuntary
depression of the eyelids (producing _almost_ an appearance of sleep) in
a part of the audience, which we were at a loss to attribute to anything
but the weight of the atmosphere. Water varies in the same way. It is
hardly necessary to say that Lake Wetter derives its name from the
superior quality of its dampness.]

"2. Of the specific gravity of the air he seems to be amusingly
uncertain,--making it first 833 times and afterwards 770 times less than
that of water; and in the same connection he says, in chosen
phrase, that 'density, or _closeness_, is another quality of the
atmosphere,'--as if it were its characteristic, and not common to all
ponderable matter."

[A very neat way of arriving at specific gravity in its densest form is
to distil the "funny column" of a weekly newspaper. To arrive at the
desired result in the speediest way, let the operation be performed in
what is known among bucolic journalists as a "humorous retort." Density
and closeness should not be spoken of as equivalent terms. The former is
a common quality of the human skull, rendering it impervious; whereas a
man may be very close and yet capable of being stuck,--with bad paper,
for example.]

"3. In mentioning the _constituents of the atmosphere_, he adopts
without explanation the loose statement of some of the books, placing
carburetted hydrogen on the same footing as to constancy and amount with
carbonic acid, and making no allusion to nitric acid. Yet chemistry has
shown, that, except in special localities, carburetted hydrogen occurs
only as a slight trace, the existence of which in most cases is rather
inferred than actually demonstrated, and that it has no important
office to perform,--while nitric acid shares with ammonia in the grand
function of the nourishment of plants. In a later paragraph the error is
aggravated by the assertion, that 'no chemical combination of oxygen and
nitrogen has ever been detected in the atmosphere, and it is presumed
none will be,'--as if every flash of lightning did not produce a notable
quantity of this compound, which, washed down by the rain, may be
detected in almost every specimen of rain-water we meet. What would
Johnstone, Boussingault, Liebig, and the other agricultural chemists say
to this?"

[For complete proof o