Agriculture . snecessary, therefore, to have the gravel well screened ; thenthe coarser part should be spread on the roadway and wellrolled, and the finer gravel spread upon it to fonm the soft material, such as sods and loose dirt, should be kept 19° AGRICULTURE. out of the gravel; in short, the gravel should be as clean aspossible; it should be screened, graded, and put on in layers,and should be well rolled. Stone Roads. —As a rule, gravel is more or less rounded,and therefore does not at first bind well. You know that aroad could not be well made out of marbles. To bind wellthe
Agriculture . snecessary, therefore, to have the gravel well screened ; thenthe coarser part should be spread on the roadway and wellrolled, and the finer gravel spread upon it to fonm the soft material, such as sods and loose dirt, should be kept 19° AGRICULTURE. out of the gravel; in short, the gravel should be as clean aspossible; it should be screened, graded, and put on in layers,and should be well rolled. Stone Roads. —As a rule, gravel is more or less rounded,and therefore does not at first bind well. You know that aroad could not be well made out of marbles. To bind wellthere must be sharp corners and rough sides on the we find that broken stone will make a stronger and moredurable road than will gravel. But we must remember thepoints already referred to, namely, the road must first of all bethoroughly drained, both underneath and on the sides; thestone must be put down in courses, the largest below and thesmallest on the surface, and every course must be thoroughly. Fig. 84.—This is the kind of road that is made by placing loose stoneson a dirt road without properly preparing the foundation—thestones sink through the mud beneath. rolled as it is laid. It is a mistake to leave the rolling untilthe road is all filled in. The dirt sub-soil should first be wellrolled. In using broken stone care should be used in choos-ing a tough rock; if the rock is soft it will soon be groundinto dust. Tough limestone and the hard rock called trapare the best. Sandstone and most kinds of granite are tooeasily crumbled for use on roads for heavy travel. Now, as to the mode of building or laying a stone of all, we may build the road of broken stones, none ofwhich are over three inches in diameter, laying the stone incourses, and well packing it by rolling. In this way we make ROADS. what is called a macadani road. It is so named after a Scottishengineer, John L. Macadam, who lived from 1756 to 183O,and who originated this method of making
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