APPLIED MECHANICS. 



[REGULATION OF POWER. 



tion canned by the rubbing together of imperfoctly- 

 HDOothed surfaces. This is tubject about which little 

 is known, or probably ever can be known. Some of its 

 general laws have been successfully investigated, and a 

 tew general principle* have been carried into practice ; 

 but iU effects vary so much with every change of mate- 

 rialof speed, pressure, workmanship, and even tem- 

 perature and other circumstance* that, after all, expe- 

 rience U the only real guide in all matters where it is to 

 be considered. Except in a few mechanical arrangements 

 where friction U employed as a useful resistance, as in 

 the case of the friction-break of a locomotive or of a 

 crane, it is generally the mechanic's object to diminish it 

 M much a* possible. The overcoming of friction is, in 

 fact, the wasting of so much power ; and as all machines 

 are devised with a view to economy in the application of 

 power, it becomes most important to reduce the waste to 

 its minimum. In all devices for communicating and 

 modifying motion, the question of friction becomes 

 nearly as important as the question of strength ; and 

 many arrangements which are ingenious, and would be 

 * table, did friction nut interfere, become compara- 

 tively useless, in consequence of its influence. 



If one who had never made mechanics his study were 

 introduced into a large manufactory, and had pointed 

 out to him the steam-engines, the cranks, levers, wheels, 

 pinions, straps, and other contrivances for communi- 

 cating power throughout the building, and setting in 

 motion each machine, he would at first be bewildered, 

 and inclined to believe that the art of communicating 

 motion was intricate and complicated ; but were he really 

 to analyse the process carefully, and trace exactly the 

 progress of the power or motion from the prime mover 

 to the last machine, he would find the whole effected by 

 the combination of a few simple mechanical elements ; 

 and wonder that through means so simple, results 

 apparently so complicated could be attained. 



Students of astronomy cannot help being struck by 

 the circumstance, that the various motions of planets, 

 satellites, and comets, and probably also of the stars and 

 nebulae, of the farthest and greatest, as well as of the 

 nearest and smallest, of the heavenly bodies, all result 

 from two simple forces, acting in various directions and 

 with different intensities. The movements of the vast 

 machine of the universe present, to a superficial observer, 

 inextricable confusion and inexplicable irregularity ; but 

 to a mind like that of Newton all is skill, order, and 

 beauty. The very disturbances to which the different 

 parts of the grand machine are subjected are elements 

 of stability ; the irregularities are sources of permanence. 

 In a system of machinery devised by human ingenuity 

 and executed by human hands, there can, indeed, be no 

 approach to this simplicity, order, and harmony ; every- 

 thing must be imperfect in proportion as man is imper- 

 fect, when compared with the Divine Mechanic of the 

 Universe. 



In every human work there mxist be elements of 

 decay, sources of irregularity, and causes of instability ; 

 and these can only be reduced by diminishing the extent 

 and complication of the work itself. Simplicity is, 

 therefore, the great aim of the mechanic, especially in 

 arrangements for communicating motion. Every wheel, 

 every lever, every pulley that can be saved, is saved 

 not so much to avoid the cost of its introduction, as with 

 a view to simplify the machinery, and thereby diminish 

 the amount of friction and wear, and increase the per- 

 manence of the whole. To the eye of a practised me- 

 chanic, therefore, the beauty of a piece of machinery 

 seems to depend more on its simplicity than on any other 

 principle. The fewer the parts required in any appara- 

 tus to render it effective, the more ingenious is its con- 

 trivance, and the less is it liable to derangement, irregu- 

 larity, and decay. 



G<"' -0 POWER -Next in order to con- 



trivances for communicating power or motion, may be 

 studied those for regulating and governing it, so as to 

 secure uniformity of action. Ail the forces we employ, 

 with the exception of gravity, are subject to continual 

 variations of intensity ; and even the most uniformly 



regulated forces, when transmitted through trains of 

 machinery necessarily imperfect, are subjected to con- 

 siderable variations. Further, the forces we employ are 

 chiefly used for effecting changes on materials ; and as 

 the qualities and conditions of the materials vary, so the 

 Quantities of force required to do the work upon 

 differ. It becomes, therefore, most important that 

 arrangements should be devised for compensating all 

 these variations of force ; and accordingly, great inge- 

 nuity has been exhibited in contrivances for that pur- 

 pose. We may quote a very beautiful specimen of 

 mechanical skill applied for a purpose of this kind, in 

 order to illustrate the great use of such arrangements. 

 Wind-power is used to a great extent for putting ma- 

 chinery in motion ; and yet, as we all know, nothing is 

 more variable than the force of wind, both in direction 

 and intensity. In former times, wind-mills were made so 

 that the miller, watching the direction of the -.. 

 could turn round the sails of his mill to face it, and furl 

 or unfurl those sails as he found the breeze too strong or 

 too light to give the velocity of movement he mii;lit 

 require. But in modern wind-mills, the wind itself is 

 made to regulate the machinery by simple but ingenious 

 arrangements. In the first place, if the wind change in 

 direction, it blows upon a small subsidiary set of sails 

 placed so that they can be acted on by a wind that does 

 not directly blow upon the main arms ; by a little si 

 machinery, this side action of the wind is made to turn 

 round the head of the mill until it brings the great sails 

 into the proper position to receive its direct iinpul*t 

 just as the wind acting on a weathercock brings the 

 arrow-point round to face it, by its pressure on the In 

 feather at the other end. Again, should the force of the 

 wind increase, this very increased force is made to act 

 upon a regulating apparatus so as to furl the different 

 divisions of the sails, or to turn the surfaces of which 

 they are made up edgeways to its impulse, and thereby 

 to diminish the surface on which it acts, proportionally 

 to its increase of intensity. The consequence of these 

 contrivances is, that from whatever quarter the wind 

 may blow, the sails of the mill are always directly opposed 

 to it so as to receive its full action ; and whatever be its 

 force, whether a gentle gale or a stiff breeze, the power 

 communicated to the machinery does not greatly vary. 

 Perhaps the most ingenious devices for regulating power 

 and velocity are those employed in apparatus for the 

 measurement of time-clocks, watches, and the like, 

 which form one most interesting branch of mechanical 

 art, Horology. 



NATURE OF MACHINES. Having obtained the 

 power necessary for our purposes, and having found the 

 means of communicating it to our machines, and of regu- 

 lating its intensity so as to suit the work to be done, we 

 have next to inquire into the nature of the machines 

 themselves, or the contrivances through which the power 

 is made to act on the inert material subjected to it. 



We can scarcely venture to offer a very distinct classifi- 

 cation of machines ; nor, indeed, in a work of limited 

 compass like the present, could we pretend to discuss in 

 I : ul, all the different classes of machinery now in use. 

 The subject is so extensive, and demands so minute a 

 knowledge of what has been done by thousands of in- 

 genious mechanics, that even the professed machinist 

 cannot pretend to an intimate acquaintance with every 

 branch of it. But the qualities of mind and the ex 

 mental training which render a man skilful and adept in 

 one or two of these branches, make it easy for him to 

 take up intelligently, any other branch that may be 

 brought under his notice. The same general mechanical 

 principles pervade all kinds of machinery, the modes of 

 applying them being varied according to the nature of 

 the material subjected to their operations, or to the kind 

 of work to be done. With the exception of certain 

 special apparatus, we believe almost all the machinery 

 used in modern times may be classed under some of the 

 following heads : 



I. Machinery for raising Weight* and girinq Pretiure. 

 Among these we may notice especially the simple 

 mechanical powers, the lever, wheel and axle, pulley, 



