266 MEGHAKIC POWER* 



Meafure of j^fj twicc the fpacc through which it fell, allowing the fame 

 niechamc power . ,. , • , . , ^ • , i • r n- • 



©refleft. ^*^^ ^or this horizontal courle as it had in tailing its perpen- 



dicular height, and that its tendency is to continue that courfc 

 forever. 



From this ftatement of the law of bodies in motion, (fo far 

 as it goes) I think we need not be very diffident in faying, 

 Ihi^t it is from limilar facts, (though lefs ph.ilofophically obferv- 

 ed) that we obtain our primary ideas of motion. The apple 

 falling from the tree is a very good infiance to the point, and 

 it would not require a very extraordinary ftretch of genius to 

 apply fuch an accident as that to any thing like the pile 

 engine, ftamping prefs, &c. 



But there are certain fpeculative mechanics, who in their mode 

 of accounting for effects like what are here flated, have chcfen 

 to adopt terms of a very different import, and for fome latent 

 reafon wiflv to keep gravitation out of fight. The writer of 

 the article Dynamics in the Supplement of the Encyclopedia 

 Britannica, calls it preffure, and by his way of philofophifing in 

 tl>e explanation of the meafure of mechanic power, has (ia 

 ray opinion) laboured to make it as myfterious as pofTible. 



I muft for the fake of thofe of your readers who have not 

 <he work to refer to, quote a fi^w paflages now and then from 

 the above popular work, and here I would r^er them to 

 the article on Machinery, where he begins by ftating, thjrf; 

 diffe,r<?nt notions have been entertained on this fubjed by 

 Leibnitz, des Cartes, and other eminent mechanics of the lall 

 century, and adds, *' that fome of the moft eminent jwaSiitionen 

 of the prefent times (for %i:e miift include Mr, Smtaton in the 

 number) have given meajures of mechanical po-j^er in machinery-, 

 ivhich ue think inaccurate and tending to erroneous conclufions 

 and maxiinsJ* -.;,.■ 



H^ then proceeds to explain and demonftrate the true 

 mealiire of mechanic power, and he begins by fuppofing, a 

 ji^an prefling uniformly on a mafs of matter lor a certain time, 

 and going on with the fubje6l takes occafion to diftinguilh 

 between the weight of a body and its keavinef ! and, towards 

 the latter end of that fedion he comes to fome fort of a con^ 

 clufion of the fubjed, fo far as to fay what is the real meafure of 

 mechanic power : I fee I muft make endlefs quotations if I 

 regard the very letter of his argument, but I hope I (hall be 

 excufedj however I will quote the laiV paragraph verbal im^ 



K elating 





