LIFE OF THE AUTHOR. XIX 



ous roof as if it had been a small weight. I attri- 

 buted this at first to a degree of strength that ex- 

 cited my terror as well as wonder ; but thinking 

 farther of the matter, I recollected that he had ap- 

 plied his strength to that end of the lever which 

 was furthest from the prop ; and finding on enquiry, 

 that this was the means whereby the seeming 

 wonder was effected, I began making levers (which 

 I then called bars ;) and by applying weights to 

 them different ways, I found the power gained by 

 my bar was just in proportion to the lenghts of the 

 different parts of the bar on either side of the 

 prop. I then thought it was a great pity that, 

 by means of this bar, a weight could be raised but 

 a very little way. On this, I soon imagined, that, 

 by pulling round a wheel, the weight might be 

 raised to any height by tying a rope to the weight, 

 and winding the rope round the axle of the wheel ; 

 and that the power gained must be just as greo: 

 as the wheel was broader than the axle was thick ; 

 and found it to be exactly so, by hanging one 

 weight to a rope put round the wheel, and another 

 to the rope that coiled round the axle. So that in, 

 these two machines, it appeared very plain, that 

 their advantage was as great as the space gone 

 through by the working power exceeded the 

 space gone through by the weight; and this 

 property I also thought must take place in a 

 wedge for cleaving wood; but then, I happened 

 not to think of the screw. By means of a turn- 

 ing lathe which my father had, and sometimes 



