[J. F. I.
U. S. Isotope Distribution.--More than 600 universities, hospitals and research laboratories in 46 states are using isotopes produced by the U. S. Atomic Energy Commission for medical, biological, industrial, agricultural and scientific research and medical diagnosis and treatment, the Commission stated in a report recently. The report, "Isotopes--A Five Year Summary of U. S. Distribution," is available to the public from the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C., for $1.00 per copy. A summary of isotope applications considered to be of significance to industry has been compiled from the Five Year Summary and printed separately as document TID-5078 available at the Office of Technical Services, Department of Commerce, Washington 25, D. C., for 30 cents per copy. The full report on isotope distribution for five years shows more than 18,900 shipments of radioactive isotopes and 1500 stable isotopes have been made to users in the United States and 1100 radioactive isotope shipments to users outside the United States. A brief summary of the growth of the isotopes program and descriptions of their uses are included in the report with a list of the users and the titles of 1400 technical reports and papers published on isotope work in the past two years. Gravity Mining of Nickel Ores.--Nature's old standby, the force of gravity, has been put to work deep beneath the earth's surface in a vast mining program that is helping maintain the free world's supply of nickel. It has given mining science the key to recovery of millions of tons of nickel-copper ore once regarded as worthless. Engineers of The International Nickel Company of Canada, Limited, at its mines in the Sudbury District in Copper Cliff, Canada, have recently adapted a mining technique by which gigantic masses of ore, far underground, are induced to cave and disintegrate of their own weight, according to R. L. Beattie, Vice President and General Manager of the company's Canadian operations. Inco's engineers took their cue from observation of the natural tendency of the lower grade ore to subside and break up after higher grade ore beneath it was mined out. Called "induced caving," this low-cost bulk mining method, plus metallurgical practices, makes it practicable for Inco to recover and treat ore lower in grade than it had ever worked in underground mining. Thus the supply of economically available ore has been broadened, aiding Inco in maintaining its current nickel production at a post-war high. In caving, a "slice" which may contain as much as 1,500,000 tons of ore is undercut. As ore from the undercut slice is withdrawn, the slice to be mined breaks away and starts to disintegrate as it moves downward, the weight of the upper part of the mass acting to crush the ore at the bottom. Another bulk mining technique by which Inco is boosting its underground production is the "blasthole" method. Blasthole mining differs from caving only insofar as explosives are used to break the slices of harder, tougher ore from the solid material. The force of gravity then takes over, as in caving. In addition to these recent innovations the company continues to use a number of other mining methods by which the higher grade ores are extracted with relatively little dilution as in the past. a