t itself, when acting upon
wings, becoming a propelling power, and so contributing to
horizontal motion."

I will collect these seven reasons for the forward motion, in the
gist of them, which I have marked by italics, that the reader may
better judge of their collective value. The bird is carried
forward, according to Dr. Pettigrew--

1. Because its wings leap forward.

2. Because its body has a tendency to swing forward.

3. Because its wings are screws so constructed as to screw
upwards and onwards any body suspended from them.

4. Because the air reacts on the under surfaces of the wings.

5. Because the wings are urged with ever-varying power.

6. Because the voluntary muscles contract.

7. Because the bird is heavy.

What must be the general conditions of modern science, when it is
possible for a man of great experimental knowledge and practical
ingenuity, to publish nonsense such as this, becoming, to all
intents and purposes, insane, in the passion of his endeavor to
overthrow the statements of his rival? Had he merely taken
patience to consult any elementary scholar in dynamics, he would
have been enabled to understand his own machines, and develop,
with credit to himself, what had been rightly judged or noticed
by others.

66. I draw it rudely in outline, as it would be set for a side-wind on
the boat you probably know best,--the boat of burden on the Lake of
Geneva (Fig. 3), not confusing the drawing by adding the mast, which,
you know, rakes a little, carrying the yard across it (_a_). Then, with
your permission, I will load my boat thus, with a few casks of Vevay
vintage--and, to keep them cool, we will put an awning over them, so
(_b_). Next, as we are classical scholars, instead of this rustic stern
of the boat, meant only to run easily on a flat shore, we will give it
an Attic [Greek: embolon] (_c_). (We have no business, indeed, yet, to
put an [Greek: embolon] on a boat of burden, but I hope some day to see
all our ships of war loaded with bread and wine, instead of artillery.)
Then I shade the entire form (_c_); and, lastly, reflect it in the
water (_d_)--and you have seen something like that before, besides a
boat, haven't you?

[Illustration: FIG. 3.]

There is the gist of the whole business for you, put in very small
space; with these only differenc