OUTLINES OF NATURAL PHILOSOPHY. 



From two of the angles of the triangle, draw lines bi- 

 secting the opposite sides. Their intersection is the 

 centre of gravity. 



Each of these lines is divided by the point of intersec- 

 tion, in the ratio of 2 to 1. 



116. To find the centre of gravity of a given py- 



Draw a straight line from the vertex to the centre of 

 gravity of the base, and divide it in the ratio of 

 three to one, the greatest segment being next the 

 vertex. The point so found is the centre of gravi- 

 ty of the Pyramip!. 



This construction applies to a pyramid of any num^ 

 ber of sides, anq. therefore also to a Cone. 



117. To find the centre of gravity of any plane 

 mechanically. 



Suspend it by a given point in or near its perimeter^ 

 and when it is at rest, draw across it a vertical line 

 passing through that point. Suspend it in like man- 

 ner by another point, and draw a vertical line as be- 

 fbrs. Tl>e intersection of these lines is the centre of 

 gravity of the plane. 



If the body is of three dimensions, the same process 

 may be followed ; but three suspensions will be ne- 

 cessary. 



This construction is referred to by PAPPUS ALEXAX- 

 DRINUS, Collect. Math. Lib. vm. Prop. i. 



Qf 



