ON THE MAKING AND FORMATION OF GRAVfil WALKS. 12? 



With regard to the thickness which gravel ought to he applied. 

 Miller has recommended from ten to twelve inches. Some subse- 

 quent authors say from ten to fourteen, and others again from five 

 to six inches thick. The numerous gravel beds which are dis- 

 persed over the country, though consisting of substances very 

 similar in their nature, are exceedingly various in their relative 

 proportions to each other. In one bed we may perhaps find sand 

 and small pebbles to prevail, in another pebbles and clay predo- 

 minates, with very little sand ; while in a third, we may probably 

 find both sand* pebbles, and clay, all blended together in pretty 

 equal proportions. As the kind of gravel to be used can, therefore, 

 seldom be a matter of choice, it needs but little argument to prove 

 the impropriety of always applying it the same thickness, without 

 regard to the quality. In confirmation of this statement, I may 

 mention as an instance, that the gravel found in this neighbour- 

 hood, though somewhat defective in colour, is in other respects 

 equal to Kensington gravel, which has been said to be the best in 

 the world ; yet, if the gravel there be applied twelve or even si\ 

 inches thick, it becomes as impervious to wet as if puddled on pur- 

 pose to retain the water on the surface : and this must necessarily 

 be the case with all gravels of a binding nature, when used in too 

 great a quantity. If the thickness be properly adjusted to the 

 nature of the gravel, a heavy shower will pass readily through to 

 the substratum below, without appearing to accumulate on the 

 surface of the walk ; and if walked upon immediately after the 

 shower, the gravel ought not to stick to the shoes, nor the least 

 impression of the feet be left in the walk behind. Gravel that 

 contains much clay will require to be used thin, and such as con- 

 tarns but little clay in proportion to the sand and pebbles, wilj of 

 course require to be thicker, in order that it may set and become 

 hard. When binding gravel cannot be obtained, river sand and 

 pebbles mixed with clay previously dried and pounded, to cause U 

 to blend with the other materials, will form a tolerably good sub. 



Mitllte. 



When walks are steep, and liable to be washed by heavy rains, 

 1 have found a kind of wooden spout or trough (Fig. 2), when 

 placed across the walk and sunk level with the gravel, to be a very 

 excellent preventive. The two sides (e e) are formed of strong 

 oak boards seven or tight inches deep, half an inch apart at the 



