Wagon roads crossing the country may be scanned for traces of the “smut” or “blossom.” This is the decomposed outcrop, which has become mingled with the soil, and may be more readily distinguished in the bed of a traveled road than elsewhere. Other surface indications failing, the topographical features of this section of country should be studied. Wherever the coal seams come to the surface, being softer than the rock strata above and below them, they are disintegrated and eroded more rapidly by the action of the atmosphere and the elements. This wearing away of the exposed coal leaves the surface outline in the form of a bench or terrace, which follows the line of the outcrop. And this form is retained even with a thick deposit of soil over the edges of the strata. Small shafts may be sunk or tunnels driven through this thickness of earth, and the outcrop explored in this way. This process of examination is of more value in the bituminous than in the anthracite regions, since the bituminous coal, being soft, is more rapidly eroded, and the terrace formation resulting from such erosion is more distinct and certain. In these days, in the anthracite coal fields, there is hardly an area of any great extent in which mines have not been actually opened. These mines, therefore, in the facilities they afford for studying exposed strata and developed coal seams, offer the best means of acquiring knowledge concerning the coal beds of adjoining tracts. In a country where no surface indications of coal are found over a large area, it is hardly worth while to explore for it by boring. In the anthracite regions of Pennsylvania the limits of the coal beds are now so accurately defined that it is seldom necessary to bore for the purpose of testing the presence of coal. But it is always advisable, before opening a mine in a new field, to test the depth, dip, and quality of the coal and the character of the seams by sinking one or more bore holes. Surface measurements of a seam are, at best, very uncertain, as indications of its continuing character. The angle of dip may change radically before a depth of one hundred feet shall be reached. And coal undergoes so great deterioration by long exposure to the atmosphere that, in order to judge the quality of a coal bed, it is necessary to have a specimen fragment from it that has been hidden away in the rocks. Hence the necessity of boring.