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Roads . 
immediately upon it, than by smaller stones, such as necessarily 
form the surface of paved roads, for the sake of procuring a tole- 
rably regular plane upon which to travel. This idea has after- 
wards been strengthened by the economy of the practice ; the 
quantity of labour in breaking the stone being thereby diminished 
But the expectations both of utility and economy are perfectly fal- 
lacious. In the first place, nothing is so certain, as that the large 
stones, let them be ever so carefully laid out at the bottom, will, 
in time, come up to the top, and that the small stones will all go 
to the bottom : and this effect will take place, sooner or later, ex- 
actly in the proportion in which the road is much, or little, used ; 
and also in the proportion in which the size of the large stones 
exceeds that of the small ones. At first sight this may appear 
extraordinary, but the effect is natural and unavoidable. It occurs 
thus : A heavy load presses upon the new road, and of course 
moves all the stones down to the lowest (B), the small stones at 
the top descend into the interstices, which are thus opened. Every 
new pressure and motion continues this process. If the lower stra- 
tum consists of stones which are large and flat, they will get to the 
top sooner than round stones. A very familiar example will eluci- 
date this process. Every housekeeper, in breaking a loaf of sugar, 
shakes the broken pieces in a box. Those that are too large, soon 
come to the top and are broken smaller. In shaking cliesnuts in 
a basket, the largest will soon be at the top, and exactly on the 
same principle. If it were not invidious, I would point out seve- 
ral turnpike roads, or parts of turnpike roads, in Maryland and 
Pennsylvania, which prove the truth of this fact. As to economy, 
(C) the calculation is in the next place quite as bad a one. Such 
a road soon wants repair, and no repair, excepting- that of breaking 
up the large stones as fast as they: appear, is an adequate one. 
These large stones necessarily range themselves on each side of 
the ruts, until they work themselves loose, and then they lie in the 
horse path. Such a turnpike is soon fit only for slow heavy wag- 
gons, and for those it is a very bad one. 
Now in the United States’ road, the lower stratum of stones 
will consist, at an average, of pieces weighing each more than 12 
times as much as each of the pieces that constitute the upper stra-. 
turn : or in other words, that have more than 1 2 times the volume, 
or bulk. Of course, many years will not elapse, before this road 
will be exceedingly out of repair and covered with loose stones of 
an average diameter of seven inches. In a level country this 
would be a less evil than among the mountains. Every obstruction 
