(34.) 
Great Me- 
chanical 
inventions 
presume a 
knowledge 
of physical 
, laws 5 
(35:) 
and gene- 
rally an in- 
ductive 
process. 
808 
mechanical skill, are both indispensable to make a 
telescope. A telescope then, though a mechanical 
invention, inasmuch as it is a deduction from phy- 
sical principles, not an addition to them, is yet a 
deduction so ingenious—so far from obvious—so im- 
possible to be conceived accidentally or by a loose 
thinker, and so easily made theinstrument of innumer- 
able discoveries of the highest novelty and grandeur, 
that no historian of science ever thought of omitting 
the invention of the telescope, or of giving it an im- 
portance inferior to that of a discovery, containing as 
it did the germ of so many discoveries. In like manner 
a theory of optics might be written in which a tele- 
scope need never be mentioned; but would not the 
pedantry of such a work be obvious, or would any 
reasonable person wish to learn science after such a 
fashion ? 
The clear co-ordination of the parts of an invention 
towards the attainment of a given result, with a due 
regard to natural laws, and the properties of the sub- 
stances used, constitutes the merit of the invention ; 
and this merit may be irrespective of the precise im- 
portance of the end of the invention, which may be 
intended to promote science, or commerce, or con- 
venience, or even to satisfy mere curiosity. A tele- 
scope would have been a telescope still, could we have 
imagined it invented with no other object than a deer- 
stalker’s sport ; and so contrivances which in their ori- 
gin and application seem remote from scientific uses, 
constitute nevertheless real steps in the progress of 
knowledge. The steam-engine is one striking ex- 
ample. Originally devised with an exclusively com- 
mercial object—the extrication of the Cornish mines 
from subterranean water, it became in the hands of 
Watt, first an instrument for experiments on the re- 
lation of heat to matter; next, in its improved form, 
a beautiful exemplification of these laws, and an en- 
during monument of the sagacity and skill of its 
author, as well as the most important inorganic 
agent which exists in modifying the social condition 
of the entire globe. Finally, to illustrate the posi- 
tion from which we started, it becomes the instru- 
ment of fresh discoveries. This very engine has a 
theory to be worked out, probably unimagined even 
by its sagacious author—its operation as an agent for 
obtaining power from matter by the application of 
heat, is shown to be in all probability a single case of 
a more general law, including all kinds of machines 
and all sorts of matter; and this more general theory 
of heat as a motive power leads, once more, to new 
practical deductions, to the conditions under which 
such machines may be most usefully constructed and 
employed. 
Every instrument, every construction, which is 
founded on a theory, and in which a certain compli- 
cation of conditions is required to produce a certain 
MATHEMATICAL AND PHYSICAL SCIENCE. 
[Diss. VI. 
result; a telescope, for example, or a steam-engine, 
or a bridge, is, in the first instance at least, an ex- 
periment. Few inventions are so simple and straight- 
forward in their plan, are so independent of the seem- 
ingly capricious behaviour of matter under untried 
circumstances, or depend so entirely on physical laws 
thoroughly understood, that the inventor can await, 
without the pang—at least of impatience—if not of 
anxiety, the moment of the realization, by actual 
trial, of his hopes and his calculations. We can all 
readily imagine the throb of anxiety with which 
Galileo pointed his glasses for the first time to the 
moon—with which Watt saw the cylinder of his As in 
model exhausted, and the piston descend under the Watt's 
action of his separate condenser—and Stephenson 
the stupendous iron tube at Conway resting for the 
first time straight as a ramrod on its two piers— 
these are moments of anxiety and of triumph, which 
place the inventor of a machine and the architect of 
a structure on a par with the discoverer of a planet, 
or with the author of a theory. ‘‘ Whenever an ori- 
ginal mind produces new combinations of thought and 
feeling,’’ says Sir James Mackintosh, with equal im- 
partiality and truth, “ whether its means be words or 
colours, or marble or sound, or command over the 
mighty agents of nature; whether the result be an 
epie poem, or a statue, or a steam-engine, we must 
equally reverence those transcendent faculties to which 
we give the name of genius.”? It is almost needless 
to add the caution, that such praise is only applicable 
when the invention is such as to call forth the qua- 
lities which distinguish the Philosopher. It is not 
the mere command over the agents of nature which 
challenges our admiration, it is the foresight, the 
patience, the conceptive faculty, the clear-sighted 
and confident anticipations of what will be the re- 
sults of natural laws acting in given circumstances, 
these circumstances being in some essential particu- 
lars new. Merely to adopt known contrivances, 
where experience has already anticipated the result, 
may exercise judgment, but hardly genius; and to 
make contrivances in which the result depends rather 
upon laws of geometry than of physics, hardly come 
within the scope of these remarks. 
Watt’s Parallel Motion, perhaps the most inge- 
nious of his inventions, would not have made a great 
reputation ; nor does the endless variety of machines 
used in the arts, as in spinning, printing, and paper- 
making, stand higher. It is when the inventor 
places Matter in new relations to Force, or derives 
power from new sources, or teaches Light or Electri- 
city to act under new conditions, that he becomes 
really a Mechanical Philosopher. 
steam-en- 
? gine. 
(36.) 
It is not given to man to endue matter with new  (87.) 
properties, or to prescribe the laws under which his The limits 
inventions are to take effect, A new motive power, 
1 See Carnot, Puissance Motrice du Feu, and the writings of M. Clapeyron, Professor W. Thomson, &c. 
2 Speech at a meeting for erecting a monument to Watt, in Arago’s Eloge of Watt. 
