"It is a simple task to break stone for macadam roadways, and by the aid of modern inventions it can be done cheaply and quickly. Hand-broken stone is fairly out of date and is rarely used in America where any considerable amount of work is to be undertaken. Stone may be broken by hand at different points along the roadside where repairs are needed from time to time, but the extra cost of production by this method forbids its being carried on where extended work is undertaken. Hand-broken stone is generally more uniform in size, more nearly cubical in shape, and has sharper angles than that broken by machinery, but the latter, when properly assorted or screened, has been found to meet every requirement.
"A good crusher driven by eight horsepower will turn out from forty to eighty cubic yards of two-inch stone per day of ten hours, and will cost from four hundred dollars upward, according to quality.
"Some crushers are made either stationary, semistationary, or portable, according to the needs of the purchaser, and for country-road work it is sometimes very desirable to have a portable crusher to facilitate its easy transfer from one part of the township to another. The same portable engine that is used in thrashing, sawing wood, and other operations requiring the use of steam power may be used in running a stone crusher, but it is best to remember that a crusher will do its best and most economical work when run by a machine having a horsepower somewhat in excess of the power actually required.
"As the stone comes from the breaker the pieces will be found to show a considerable variety in size, and by many practical road-makers it is regarded as best that these sizes should be assorted and separated, since each has its particular use. To do this work by hand would be troublesome and expensive, and screens are generally employed for that purpose. Screens are not absolutely necessary, and many road-makers do not use them; but they insure uniformity in size of pieces, and uniformity means in many cases superior wear, smoothness, and economy. Most of the screens in common use today are of the rotary kind. In operating they are generally so arranged that the product of the crusher falls directly into the rotary screen, which revolves on an inclined axis and empties the separate pieces into small bins below the crusher. A better form for many purposes includes a larger and more elaborate outfit, in which the stone is carried by an elevator to the screen and by the screen emptied into separate bins according to the respective sizes. From the bins it is easily loaded into wagons or spreading carts and hauled to any desired point along the line of the road.