WEI 



Cor. 1. If the wedge be isosceles, A D D B,and if resistances act at 

 equal angle's, 



p - R 4. R, " AB 9AP 



' ' sin. L P M ' sin. F R j' 

 Cor. 2. If power act at right /s to the back, P : R -f- R' : : .* 



of wedge X sin. 



AD_ . sin. * ^of wedge r .. . 



TFR~E " ~~7 * s. FRE " 



F R E : (rad.)*. 



Cor. 3. If the resistances in the last Corel- A 

 lary act perpendicularly on the sides of the 

 wedge, P : R -f- R' :*. A C : A D. If the di- 

 rections of the resistances be perpendicular 

 to the back, P : R -f R' : : A C 2 : A D. And 

 lastly, if they act parallel to the back, P ; 



R + R' : : c E : A D. 



Cor. 4. la the demonstration of the proposition, it has been supposed 

 that the sides of the wedge are perfectly smooth ; if, on account of the 

 friction, the resistances C F, C/are wholly effective, we have 

 P : R -f- R' : : sin. C F/, or F C A : rad. 



The power applied to the wedge is usually percussion, and almost the 

 only instance in which it is used for the purpose of equilibrium is in tho 

 construction of arches, built of truncated wedges. 



WEIGHTS and Measures, Tables of. 



Grains. 

 24 



480 



5760 



WEIGHTS. 

 TROY WEIGHT. 



~~~~~ 1 Pennyweight. 



~~, 20 ~ 1 Ounce. 



~~~~ 210 ,~~.~~ 12 sw~r* 1 Pound. 



By this weight, gold, silver, jewels, and precious stones are weighed. 

 It is also used for ascertaining the strength of spirits, for experiments in 

 Nat. Philosophy, and for comparing the different weights with each other. 



Standard gold consists of 22 parts of fine gold, and 2 parts of alloy j and 

 standard silver contains 37 parts of fine silver, and 3 of alloy. 



The standard price of gold is 3. 17*. 10}d. per ounce, or 45. Us. 6d. 

 per pound, a pound being coined into 44% guineas. A pound of standard 

 silver is now coined into 66 shillings, instead of 62 shillings, as formerly. 

 339 



