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POPULAR SCIENCE REVIEW. 
sideration that tlie simplest phenomena are often those which 
exhibit in their most intelligible form the grandest and most 
important laws of nature ; and obvious as the fact may seem 
that the man who attempted to work a steam-engine without 
supplying coal for its fire would stand but little chance of 
seeing its wheels revolve, it is doing no injustice to the 
majority of our readers to suppose that they have never asked 
themselves what the fuel really does in such a case as this, 
and why it is so essential to the production of steam ? It is 
probable that the idea may never have suggested itself to them 
that these, and dozens of other instances of a similar kind 
which might be quoted, all go to show that without the 
disintegration, or waste, of some form of matter, whether it 
be coal, or metal, or tallow, or gunpowder, there is no produc- 
tion of any form of force, no real acquisition of power of any 
kind. And, like Columbus's egg, simple as this truth may 
seem when once clearly demonstrated, and often as men have 
lighted fires to warm themselves by, and long as they have 
employed the explosive properties of gunpowder to carry 
conviction to the minds of their intelligent fellow-creatures, it 
is only quite in recent years that its reality has come to be 
distinctly recognized, and that we have begun to learn that 
perpetual motion, and other patent processes for extracting 
something out of nothing, are ideas worthy only of the sages 
of Laputa. 
It may, however, be said, that all exhibitions of force do not 
involve a waste of matter. We may be told, for instance, that 
the stream of falling water which turns the river-side mill exerts 
its power on the mill-wheel in virtue of the force of gravitation 
which draws the water downwards, and that gravity is a force 
which, so far as we can see, does not involve the waste of 
matter as a condition of its manifestation. But this is an 
exception which is probably more apparent than real, and 
which is due rather to our ignorance of the nature of gravi- 
tation than to any deviation from a law which so unquestion- 
ably obtains in the vast majority of phenomena with which we 
are acquainted. For it is by no means unlikely that gravity, 
which is itself a cosmical force, acting through space upon the 
most distant elements of the universe, may be the local mani- 
festation in our world of disturbances in the relations of 
matter going on in spheres existing at infinite distances 
from it. 
The propulsive force, too, of the breeze by which the ship 
is driven through the resisting waves, at first sight appears to 
be a case of force exerted independently of matter or its rela- 
tions. But here again the exception is only apparent and not 
real. For science tells us that that breeze is the offspring of 
