H N LECTURE I. 



has often been inaccurately treated: the consideration of cordage leads us to- 

 that of union by twisting, and by intermixture of fibres; including the im- 

 portant arts of carding, combing, spinning, ropemaking, weaving, fulling, 

 felting, and papermaking; which constitute the employment of many mil- 

 lions of manufacturers, of all ages and sexes, in every part of the world, and 

 by which the animal and vegetable productions of a large portion of the sur- 

 face of the globe, are made to contiibute, as well to. the power and riches of 

 the individuals wlio supply them, as to the health and comfort of the public 

 that consumes them. The admirable art of the watch and clock maker is a pe- 

 culiarly interesting department of practical mechanics, it affords employment 

 for mathematical investigation, for experimental inquiry, and for ingeni6us in- 

 vention; and the perfection, wliich it has derived from a combination of these 

 means, does honour as well to the nations who have encouraged it, as. to the 

 individuals who have been engaged in it.. 



To counteract the powers of gravitation and of friction, is the object of 

 such machines as are vised for raising and removing weights : cranes, friction 

 wheels, and carriages of all kinds, are referable to this head, and some of 

 them have been the subjects of much speculation and experiment. Lastly, to 

 overcome and to modify the corpuscular forces of cohesion and repulsion, and 

 to change the external forms of bodies, is the object of machinery intended for 

 compression, extension, penetration, attrition, trituration, agitation, and de- 

 molition. For these purposes we employ presses, forges, rolling, stamping, 

 coining, and milling machines;, the processes of digging, ploughing, and 

 many other agricultural arts; boring, mining, grinding, polishing, and turn- 

 ing; mills of various kinds, threshing mills, corn, mills, oil mills, and powder 

 mills; besides the chemical agents concerned in blasting rocks, and in the opei*^ 

 ations of artillery. All these arts are comprehended in the department of me- 

 chanics, which constitutes the first division of this course. Not that we shall 

 be able to enter at large into the detail of each; but having formed a general 

 outline, we may fill up its particular parts with more or less minuteness, as 

 we may find more or less matter of importance to insert in each ; and those 

 who wish to pursue the subjects further, will every where be able to derive 

 great assistance from the authors whose works will be mentioned. 



The doctrines of hydrodvnamics relate to the motions and affections of 



