n this head, be struck by lightning. For
ourselves, we are convinced, and would rather have some other head
taken for an experiment by way of illustration. But any of our
readers who is unsatisfied has only to place himself in front of a
lightning-express-train with an ordinary conductor. To insure being
struck, let the experimenter provide himself amply with patent
safety-rods. At least, this result is pretty sure in houses, and is
worth trying out of doors.]

"In the same connection he characterizes nitrogen as a substance 'not
condensible under fifty atmospheres,' leaving the reader to infer
that the preceding ingredient on the list, oxygen, is condensible
(liquefiable) within that limit of pressure, and that nitrogen becomes
liquid at or above it; whereas neither oxygen nor nitrogen has ever yet
been compressed into a liquid, although a force of more than _fifty
times fifty_ atmospheres has been brought to act upon them."

[We consider an experiment requiring twenty-five hundred atmospheres,
when the thermometer marks 93 deg. in the shade, indictable at common law.
To desire more than one, under such circumstances, is unreasonable, and
even wicked.]

"4. In referring to the Thermo-barometer as a means of measuring
heights, the writer confounds the late Professor Edward Forbes with
Professor James D. Forbes, recently of Edinburgh, but now Provost of
the University of St. Andrews. The former was a great Zooelogist and
Botanist, and did not occupy himself with investigations in Physics;
the latter is an eminent Physicist, the author of the viscous theory of
Glaciers; and it is he who made the observations here ascribed to the
'Professor Forbes, whose untimely death the friends of science have
had so much reason to deplore.' The author adds the further mistake
of supposing that the numerical constant, 549 feet for each degree,
determined by James Forbes for Scotland, is equally correct for all
latitudes."

[This hardly needed confutation. No university requires any numerical
constant of height as qualification for a degree; and if they did, 549
feet would be excessive, unless, perhaps, at Warsaw, where everybody is
tall enough to end in _ski_.]

"5. Our essayist discloses but an imperfect inkling of knowledge on the
subject of capillarity in barometers, when he speaks of this complex
action as equivalent to _the attraction between the mercury and the
glass tube_; and he commits a yet graver mistake, practically sp