10 



MATHEMATICAL AND PHYSICAL SCIENCE. 



[Diss. VI. 



(34.) 



Great Me- 

 chanical 

 inventions 

 presume a 

 knowledge 

 of physical 

 laws; 



(35.) 



and gene^ 

 rally an in- 

 ductive 

 process. 



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 the instrument 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. 1 



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 



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 ' 8 

 action of his separate condenser and Stephenson, g^"' 

 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 jneans be words or 

 colours, or marble or sound, or command over the 

 mighty agents of nature ; whether the result be an 

 epic poem, or a statue, or a steam-engine, we must 

 equally reverence those transcendent faculties to which 

 we give the name of genius." 2 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- (36.) 

 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. 



It is not given to man to endue matter with new (37.) 

 properties, or to prescribe the laws under which his The lim te 

 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. 

 3 Speech at a meeting for erecting a monument to Watt, in Arago's Eloge of Watt. 



