e hot carbon monoxide passing over the hot magnetic oxide
quickly reduces it down to metallic iron, which, being in a spongy
condition, acts more freely on the steam during later makes than it
did at first, and being infusible at the temperature employed, may be
used for a practically unlimited period.

What more simple method than this could be desired? Here we have the
formation of the most valuable of all fuel gases at the cost of the
coke and steam used, a gas also which has double the carrying power
for hydrocarbon vapors possessed by coal gas, while its combustion
gives rise to nothing but water vapor.

In this course of lectures I have left much unsaid and undone which I
should have liked to have had time to accomplish, and if I have been
obliged to leave out of consideration many important points, it is the
time at my disposal and not my will which is to blame. And now, in
conclusion, I wish to express my thanks to my assistants, Messrs. J.A.
Foster and J.B. Warden, who have heartily co-operated with me in much
of the work embodied in these lectures.

* * * * *

STEREOSCOPIC PROJECTIONS.

The celebrated philosopher Bacon, the founder of the experimental
method, claimed that we see better with one eye than with two, because
the attention is more concentrated and becomes profounder. "On looking
in a mirror," says he, "we may observe that, if we shut one eye, the
pupil of the other dilates." To this question: "But why, then, have we
two eyes?" he responds: "In order that one may remain if the other
gets injured." Despite the reasoning of the learned philosopher, we
may be permitted to believe that the reason that we have two eyes is
for seeing better and especially for perceiving the effects of
perspective and the relief of objects. We have no intention of setting
forth here the theory of binocular vision; one simple experiment will
permit any one to see that the real place of an object is poorly
estimated with one eye. Seated before a desk, pen in hand, suddenly
close one eye, and, at the same time, stretch out the arm in order to
dip the pen in the inkstand; you will fail nine times out of ten. It
is not in one day that the effects of binocular vision have been
established, for the ancients made many observations on the subject.
It was in 1593 that the celebrated Italian physicist Porta was the
first to give an accurate figure of two images seen by each eye
separately,