which circulates in obedience to planetary laws;
hence, the entire mass of the zodiacal light must
be constantly approaching, and incessantly raining
its substance down upon the sun.

It is easy (for those who know how) to
calculate both the maximum and the minimum
velocity imparted by the sun's attraction to an
asteroid circulating round him. The maximum
is generated when the body approaches the sun
from an infinite distance, or perpendicularly; the
entire pull of the sun being then exerted upon
it. The minimum is that velocity which would
barely enable the body to revolve round the sun
close to his surface. The final velocity of the
former, just before striking the sun, would be
three hundred and ninety miles a second; that
of the latter, two hundred and seventy-six miles
a second. The asteroid, on striking the sun
with the former velocity, would develop more
than nine thousand times the heat generated
by the combustion of an equal asteroid of solid
coal; while the shock, in the latter case, would
generate heat equal to that of the combustion
of upwards of four thousand such asteroids. It
matters not, therefore, whether the substances
falling into the sun be combustible or not; their
being combustible would not add sensibly to the
tremendous heat produced by their mechanical
collision.

These, then, are the hammers with which the
sun is beaten, the projectiles with which he is
pelted into a white heat. Here we have an
agency competent to restore his lost energy,
and to maintain a temperature at his surface
which transcends all terrestrial combustion. In
the fall of asteroids we find the means of
producing the solar light and heat. It may be
contended that this showering down of matter
necessitates the growth of the sun; it does so:
but the quantity necessary to maintain the
observed calorific emission for four thousand years,
would defeat the scrutiny of our best
instruments. If the earth struck the sun, it would
utterly vanish from perception; but the heat
developed by its shock would cover the
expenditure of a century.

Five years after the publication of Mayer's
essay, Mr. "Waterston sketched, independently,
a similar theory at the Hull meeting of the
British Association. The transactions of the
Royal Society of Edinburgh for 1854 contain
a Memoir by Professor Thomson, in which that
sketch is fully developed. He considers that
the meteors, which are to furnish stores of
energy for our future sunlight, lie principally
within the earth's orbit, and that we see them
there, as the zodiacal light, "an illuminated
shower, or rather tornado, of stones."
Professor Thomson gives, amongst other curious
calculations, the heat wliich would be
developed by each of the planets falling into the sun.
Thus, if the planet Mercury were to strike the
sun, the quantity of heat generated would cover
the solar emission for nearly seven years; while
the shock of Jupiter would cover the expenditure
of thirty-two thousand two hundred and
forty years. Our earth would furnish a supply
for ninety-five years; while the total heat
produced by all the planets falling into the sun
would cover the emission for forty-five thousand
five hundred and eighty-nine years.

Professor Tyndall modestly adds, that his
summary conveys no adequate idea of the
firmness and consistency with which Dr. Mayer has
applied his principles. The professor does not
pledge himself to the theory, nor does he ask
Iris audience or his readers to accept it as
demonstrated; still, it would be a great mistake
to regard it as chimerical. It is a noble
speculation: and, he assures us, the true theory,
if this, or some form of it, be not the true one,
will not appear less wild or less astounding.

Whatever be the ultimate fate of the theory,
it is a great thing to be able to state the
conditions which certainly would produce a sun,—
to be able to discern in the force of gravity,
acting upon dark matter, the source from which
the starry heavens may have been derived. For,
whether the sun be produced and his emission
maintained by the collision of cosmical masses,
or not, there cannot be a doubt as to the com-
petence of the cause assigned to produce the
effects ascribed to it. Solar light and solar heat
lie latent in the force which pulls an apple to
the ground.

DUFFERS.

THE word "duffer" has now become incor-
porated in the English language, and, like many
other words that have had a similar origin, has
acquired a peculiar force of signification. It is
a word of much meaning, and well adapted for
expressing broad and general contempt.
Originally, I believe, a duffer was a person who
made old clothes "look as good as new" by
scratching up a pile on its threadbare surface.
It is possible that this branch of trade may have
been pursued honestly enough. The clothes
may have been sold for what they were, revived
articles, in wliich case no reproach would attach
to the name of the "duffer" who revived them.
But we may well imagine—knowing the
tendencies of trade—that the cloth so revived
was frequently sold for what it was not.
Then, when the gloss began to wear off, and
the seams to show, after two days' wear, the in
itself honourable name of duffer would come to
be pronounced with quite a different emphasis:
with a strong hold of the "d," a curl of the lip,
and a lowering of the eyebrows, meaning
altogether much more than could be conveyed by
the most elaborate definition.

I believe the word, in its present state of
signification, came to us originally from the
East—that is to say, from the haunts of the
sailors in Wapping and Ratcliff Highway. The
dishonest duffer would naturally commence
practice among the simple-minded, free-hearted tars.
Jack's alive to everything but the wiles of the
land shark; but when he does detect him, his
honest indignation finds appropriate and forcible
expression. My theory is, that Jack first gave the