92 CENTRE OF GRAVITY. 



higher, and consequently swings more than in an 

 unloaded horse, those twists at the double curva- 

 ture of the steep hiil, occur in many places where 

 the old line has been preserved, and among other 

 places, just near the top of Highgate Hill ; and 

 it is a fact, that though those twists are danger- 

 ous for carriages they are easier for those who walk, 

 or ride slowly, than if the road went straight up. 



Any one may convince himself of the truth of 

 these effects of the centre of gravity by trying to 

 run in a horizontal direction round a hill, without 

 getting farther from the summit or centre of the 

 hill ; or how difficult it is to run round on the 

 slope of a circular basin or hollow without getting 

 nearer to its centre or bottom. If the battlements 

 of a circular tower which has no parapet, slope 

 outwards, it is not only difficult but highly dan- 

 gerous to walk fast round them, but if they slope 

 inwards, they are safer and more easy than if one 

 were walking in a straight path having the same 

 width. Upon a similar principle though there the 

 forward motion of the centre of gravity has more to 

 do in the matter if a circular turn in a road slope 

 outwards, a coach, if moving rapidly, is apt to 

 be overturned or the passengers flung off towards 

 the outside, but if, on the contrary, the road at 

 such a place slope inwards it is safer than if it 

 were level. On this principle coaches are much 

 more endangered by passing rapidly loops of road 

 at the hips of hills, than similar loops at the heads 

 of vallies. Thus, we perceive, that there is no 

 little information even in that which to those who 

 " see things but do not look at them" appears to 

 be a merely accidental path, and that should lead 

 us to be careful to " look at every thing we can 



