April, I916.]
CURRENT ~['OPICS.
5!)5 substantial economies that materially improve the market value of this particular kind of scrap. In the first place, he made it possible to save in space something like 8o or 9o per cent., so that the waste materials, when ground up, occupy approximately about one-tenth the room ordinarily needed for turnings as they come from lathes.
Owing to its reduced bulk and lowered storage charges it brings better prices from the purchaser. It can be readily freed of oil by means of centrifugal separators, and that iron and steel scrap in this form can be separated magnetically from other scrap material is an advantageous factor in its preparation for further use.
In general design it resembles the common type of vertical conical hopper grinder. If desired, a magnetic separator can be attached. The largest amount of scrap dealt with by one of the Philipp cutters was some 77oo pounds of manganese copper turnings disposed of in 20 minutes. A 25-horse-power direct-current motor was employed. It was found, after a six months' trial, that the entire cost of using the Philipp apparatus did not exceed 32 cents per ton of scrap cut up. But subsequent use proved that the average cost of the service per ton was less than 24 cents.
Road-building Rock Tests. ANO.',,. (United States Department of Agriculture. Office of Information, March I7, 1916.)-Counties or communities intending to build water-bound macadam roads run considerable risk of failure unless they have the rock they are to use tested for hardness, toughness, and binding power. These are the qualities, in the opinion of the engineers of the Office of Public Roads and Rural Engineering, United States Department of Agriculture, which experience has shown to be most essential to the endurance of a road. The use of rock suited to withstand the wear of traffic is regarded as so important that the United States Department of Agriculture offers to test samples of road-building rock for any citizen free of charge, provided that the samples are sent prepaid and are submitted in accordance with definite printed instructions. These instructions will be mailed by the Office of Public Roads and Rural Engineering in that department to whoever requests a copy. When a community is considering using a local stone or other stone which has not already proved its durability on highway work, the highway supervisors would do well to secure a laboratory report from the Department. These laboratorv tests are conducted with elaborate apparatus, and, in the case of'untried rock, are the only practical safeguards against the employment of material that will wear out too quickly to prove a good investment.
Engineers having to do with road-building material, or road officials contemplating the establishment of a laboratory for testing the rock used on their highways, will find that Bulletin No. 347 contains full details as to the apparatus needed and the exact methods of procedure in the case of their tests, as well as those for determining the specific gravity and water-absorbent qualities of the rock.
VOL. I8I, NO. m84--42