WED 



VOLCANOES. 



Thfltotiilniirober- of Volcanoes knowa is about 205, of which Europe 

 contains 13 or 14. Of the whole number, it is computed that 107 are in 

 islands, and 98 on the great continents. The most remarkable are JEtna, 

 Vesuvius, the Lipari islands, Iceland, Kamschatka, Japan, and so along 1 

 the eastern coast of Asia and the Indian islands ; Cape Verd, Canary, 

 and other African islands ; an immense range of them, at least 60 ia 

 number, running from north to south on the Continent of America, and 

 Occupying the summits of many of the Andes, as well as the ^Jexican 

 and Cjilifornjan_ridges ; for a few of the principal of which, see Moun- 

 tains, height of. 



URANUS, or Georgium Sidus.See Planets, elements of. 



W. 



WATER boiling, temperature of. See Heat, 

 WATER, expansion of. See Heat. 

 WATER MILL. Se<? Wheel. 

 WAVES, motion of. See Siphon. 

 WEDGE. 



1. When three forces, acting perpendicularly upon the sides of a sca 

 lene wedge, keep each other in equilibrio, they are proportional to thosa 

 sides. 



Cor. When the directions of the forces are not perpendicular to the 

 Bides, the effective parts must be found, and there will be an equilibrium 

 when those parts are to each other as the sides of the wedge. 



2. In general let A B C represent a 

 section of the wedge, and let a power 

 P, represented in magnitude and di- 

 rection by L P, act upon A B the 

 back of the wedge, and let it be coun- 

 teracted by two resistances R and R', 

 which are represented in quantity 

 and direction by F R,/r ; then when 

 the wedge is at rest, 



p R 4. R - _A2_ _AEL_ JL BD 



' ' tin. L P M ' Bin. F R E "^ sin. fr t 

 338 



