conditions remain forever blank. The owl and bat can see when we cannot;
their eyes can receive oscillations of ether, which pass by without
affecting us. So with sound, which "is a sensation produced when
vibrations of a certain character are excited in the auditory apparatus of
the ear."[78] The longest wave which can give an impression has a length
of about 66 ft., which is equal to 16-1/2 vibrations per second; when the
wave is reduced to three or four tenths of an inch, equal to from 38,000
to 40,000 vibrations per second, sound becomes again inaudible. The piano,
for instance, only runs between 27-1/2 vibrations in a second up to 3,520.
Sound travels about 1,093 feet per second, and the human voice can be
heard 460 feet away, whilst a rifle can be heard 16,000 feet (3.02 miles),
and very strong cannonading 575,840 feet, or 90 miles. That there are
vibrations above and below 16-1/2 and 40,000, there is no room to doubt,
as there exist ears which can hear them, such as the hare; but to us they
are as though they did not exist.

Of all our senses, the sense of smell far surpasses that of the other
sense. Valentine has calculated that we are able to perceive about the
three one-hundred-millionth of a grain of musk. The minute particle
which we perceive by smell, no chemical reaction can detect, and even
spectrum analysis, which can recognize fifteen-millionths of a grain, is
far surpassed. But this sense in man is far surpassed by the hound.

Our sense of taste is also limited, and as has been already stated,
cannot distinguish all flavors. We can recognize by taste one part of
sulphuric acid in 1000 parts of water; one drop of this on the tongue
would contain 1/2000 of a grain (3/400 of a grain) of sulphuric acid.
The length of time needed for reaction in sensation has been determined
by Vintschgau and Hougschmied, and in a person whose sense of taste was
highly developed, the reaction time was, for common salt, 0.159 second;
for sugar, 0.1639 second; for acid, 0.1676 second; and for quinine,
0.2351 second.

Reviewing, then, the above, it is evident there are eyes which can see
what we cannot, there are ears which can hear what we cannot, and there
are animals who can smell and touch what we cannot. "For anything we
know to the contrary, then," says Savage, "a refined and spiritualized
order of existences may be the inhabitants of another and unseen world
all about us." As Milton has said:

"Millions of spirit