3-8 St hemes for Ptrpeluat Molten. 



wcijjlit B hath already run out be admitted, it will then remain a queftion whether thcfe 

 two exterior weights, B and C, can preponderate over tlie four inner weights K L M A. 

 The more accurate examination of this particular contrivance will lead to the following 

 theorem. In two concentric circles, if tangents be drawn at the extreme points of a dia- 

 meter of the fmaller, and continued till they intcrfefl the larger, the common centre of 

 gravity of the arc of the greater circle iniluded between the tangents, and of the half pe- 

 riphery of the fmaller circle on the oppofite fide of the diameter, will be the common centre 

 of the circles. If, therefore, the balls were indefinitely numerous and fmall, the fuppofeJ 

 effe£live parts of the w heel, fig 5, would be in equilibrio, as well as the parts beneath the. 

 horizontal tangent of the Inner circle. 



Fig. 6 reprefents the contrivance of Dr. Shiviers, which, in a periodical publication, in 

 other particulars refpeflable, has been faid to continue in motion for weeks, and even 

 months together. There is not the fmalleft probability that it fliould continue in motion 

 for half a minute, or nearly as long as a fimple wheel would retain part of its firft impulfe. 

 The external circle denotes a wheel carrying a number of buckets, A B I L, &e. C repre- 

 fents a toothed wheel, on the fame axis, which drives a pinion D ; and this lad drives another 

 pinion E upon the axis of a lanthorn, or wheel intended to work a chain pump with the- 

 fame number of buckets as in the large wheel A B I. The lanthorn G is made of fuch a 

 (ize as to raife the buckets a b 1 1 with a due velocity. K reprefents a gutter, through 

 which a metallic ball, contained in the bucket m may run and lodge itfelf in the bucket A 

 of the wheel. Each of the buckets of the wheel B I L M, which are below the gutter, is 

 fupplied with a metallic ball, and fo likewife are the afcending buckets abilm of the 

 chain-pump. As the pump fupplies the wheel, it is itfelf again fupplied at M, where the 

 balls fall into its afcending buckets. Now it is prefumed that the balls in the wheel, I fup- 

 pofe on account of their didance from the centre of motion, will defcend w-ith more than 

 fuflicient force to raife thofe on the chain, and confequently that the motion will be 

 perpetual. 



The deception in this contrivance has much lefs feduftion than in the two foregoing, be- 

 caufe it is more eafily referred to the fimple lever. This, like the others, exhibits no profpe£l 

 of fuccefs, when tried by the fimple eonfideration of the equality of the afccnt and defeent 

 in the whole time of the rotation of a fingle ball. It may alfo he fliewn from the prin- 

 ciples of wheel work, which are familiar to artifans, that whatever is gained by the excefs 

 of the diameter of the great wheel beyond that of the wheel C, is again loll by the excefs 

 of the lanthorn A beyond the pinion E. 



The fundamental propofition of the fimple lever or balance, that equal bodies at an equal 

 didance from the fulcrum will equiponderate, but that at unequal didances the mod remote 

 will defcend, has in thefe and numberlcfs other indances led mechanical workmen and 

 fpcculators to purfue this fruitlefs enquiry with labour and expenee often ill-afforded, 

 and with a degree of anxiety and infatuation which can hardly be conceived by thofe who 

 have never fuffercd the pain of hope long deferred. For this reafon chiefly, it has appeared 

 dcfirable and ufcful to treat the fubject in a familiar way, without dcfcending to thofe ex- 

 prcfiTions of contempt, which ignorance, harmlefs to all but itfelf, is furely not entitled to. 

 If fuch reafoners were well convinced that the power of a machine is to be edimated by 

 the excefs of motion referred to the perpendicular, without any regard to the apparent 



centre 



