16 FERGUSON'S LECTURES. 



LECT. Hence appears the absurdity of people's rising hastily 



v_x-v-%J i" a coach or boat when it is likely to overset : for by 



Center of that means they raise the center of gravity so far as to 



gravity, endanger throwing it quite out of the base ; and if they 



do, they overset the vehicle effectually. Whereas, had 



they clapped down to the bottom, they would have brought 



the line of direction, and consequently the center of 



gravity, further within the base, and by that means 



might have saved themselves. 



The broader the base is, and the nearer the line of 

 direction is to the middle or center of it, the more 

 firmly does the body stand. On the contrary, the nar- 

 rower the base, and the nearer the line of direction is to 

 the side of it, the more easily may the body be over- 

 thrown : a less change of position being sufficient to re- 

 move the line of direction out of the base in the latter 

 case than in the former. And hence it is, that a sphere 

 is so easily rolled upon a horizontal plane ; and that it is 

 so difficult, if not impossible, to make things which are 

 sharp-pointed to stand upright on the point. From 

 what hath been said it plainly appears, that if the plane 

 be inclined on which the heavy body is placed, the body 

 will slide down upon the plane whilst the line of direction 

 falls within the base ; but it will tumble or roll down 

 when that line falls without the base. Thus, the body A 

 will only slide down the inclined plane C D, whilst the 

 body B rolls down upon it. 



When the line of 

 direction falls with- 

 in the base of our 

 feet, we stand; and 

 most firmly when it 

 is in the middle : 

 but when it is out of 

 that base, we im- 

 mediately fall. And 

 is not only plea- 

 sing, but even sur- 



