no 



ON THE PRINCIPLE OF LIFE> 



pelled the blood returned from the lungs into the arterial system. Whence 

 the heart itself becomes alternately a forcing and a suction pump ; being 

 the former in respect to the arteries, and the latter in respect to the veins.* 



Upon a moderate estimate, the common labourer may be said to employ 

 a force capable of raising a weight of ten pounds to the height of ten feet ih 

 a second, and continued for ten hours a day. A moderate horizontal 

 weight for a strong porter, walking at the rate of three miles an hour, is 

 200 pounds : the chairman walks four miles an hour, and carries 150 

 pounds. The daily work of a horse is equal to that of five or six men upon 

 a plane ; but from his horizontal figure, in drawing up a steep ascent, it 

 does not exceed the power of three or four men. In working windmills, 

 twenty-five square feet of the sails is equivalent to the work of a single la- 

 bourer : whence a full-sized mill, provided it could be made to work eight 

 hours a day, would be equivalent to the daily labour of thirty four men, 

 A steam engine of the best construction, with a thirty inch cylinder, has 

 the force of forty horses ; and, as it acts without intermission, will perform 

 the work of 120 horses, or of 600 men : every square inch of the piston 

 being equivalent to the power of a labourer. 



There are many muscles given to us which the common customs and 

 habits of life seldom render it necessary to exert, and which in consequence 

 grow stiff and immoveable. Tumblers and buffoons are well aware of this 

 fact ; and it is principally by a cultivation of these neglected muscles that 

 they are able to assume those outrageous postures and grimaces, and ex- 

 hibit those f^ats of agility, which so often amuse or surprise us. 



The same muscles of different persons, however, though of the same 

 length and thickness, and so far as we are able to trace, composed of the 

 same number of fibres, are by no means uniformly possessed of the same 

 degree of power ; and we here meet with an express deviation from the law 

 of physical mechanics ; as we do also in the curious fact, that whatever be 

 the power they possess, they grow stronger in proportion to their being 

 used, provided they are well used, and not exhausted by violence or over 

 exertion. 



I have calculated the average weight carried by a stout porter in this me- 

 tropolis at 200 pounds ; but we are told there are porters in Turkey, who, 

 by accustoming themselves to this kind of burden from an early period, are 

 able to carry from 700 to 900 pounds, though they walk at a slower rate, 

 and only carry the burden a short distance. " The weakest man can lift 

 with his hands about 1 25 pounds, a strong man 400. Topham, a carpenter, 

 mentioned by Desaguliers, could lift 800 pounds. He rolled up a strong 

 pewter dish with his fingers. He lifl;ed with his teeth and knees a table six 

 feet long, with half a hundred weight at the end. He bent a poker, three 

 inches in circumference, to a right angle, by striking it upon his left fore- 

 arm ; another he bent and unbent about his neck, and snapped a hempen 

 rbpe two inches in circumference. A few years ago there was a person 

 at Oxford who could hold his arm extended for half a minute, with half a 

 hundred weight hanging on his little finger."! We are also told by De- 

 saguliers of a man who, by bending his body into an arch, and having a 

 harness fitted to his hips, was capable of sustaining a cannon weighing 

 two or three thousand pounds. And not many winters ago, the celebra- 

 ted Belzoni, when first entering on public life, exhibited himself to the 



* See Stud, of Med. vol. ii. p. 19. edit, second, 

 t Young'a Lect. on Nat. Phil. i. 129. 



