32, and 39. In the same districts the number of persons to a square mile is 166, 186, 379, 1,718, 4,499, 12,351, and 63,823. Thus, in Liverpool, the densest and the unhealthiest district in England, there were 63,823 to an acre; of whom 39 per 1,000 died annually. This series of facts may be put in a different way; The nearer people live to each other the shorter their lives are. Thus the proximity of people in 53 districts is 147 yards, the mean duration of life is 51 years; in 345 districts the proximity is 139 yards, and the mean duration of life is 45 years; in 137 districts the proximity is 97 yards, and the mean duration of life is 40 years; in 47 districts the proximity is 46 yards, and the mean duration of life is 35 years; in 9 districts the proximity is 28 yards, the mean duration of life is 32 years. In Manchester district the proximity is 17 yards, and the mean duration of life is 29 years; in Liverpool district the proximity is 7 yards, and the mean duration of life is 26 years. This is a determined law, and, the duration of life being given in one set of conditions, the duration of life in another set of conditions is determined from the proximities.
An Interesting Collection of South American Fossils.—Prof. Cope bought the collection of fossil bones from the Argentine Confederation which were brought to show at the Paris Exposition. Several countries are said to have wanted them. They will be of value in this country, because the chief portion of them are not to be found anywhere in the United States. They come from Patagonia, and the collection includes about one hundred and fifty specimens of animals. There are nineteen skeletons, chiefly of large animals, almost completely whole, among which are armadilloes and sloths. One of the armadilloes has a curious tail which increases in size toward the end, at which point it takes an oval shape and is from a foot to eighteen inches wide. Unlike that of all other armadilloes, it is without joints, except that at the base. It is supposed to have been a fighting weapon. Another rare specimen is a sabre-toothed tiger, of which there is only one other known specimen in the world. The size of the sloth skeletons varies from that of a small black bear to the largest elephant. The sabre-toothed tiger and the club-tailed armadillo are supposed to have been monarchs of the forests in their day. It has not yet been determined to what institution of science the collection is to be presented.
Artificial Diamonds.—In examining the papers of their deceased father, J. N. Gaunal, Messrs. A. and F. Gaunal found one which purported to be a copy of a memoir presented by him to the Paris Academy of Sciences in 1828, and which gave an account of a process for the artificial production of diamonds. The Academy simply buried the communication in its archives, and never mentioned it in any way. The substance of this document is now published in "Le Monde de Science et de l'Industrie," from which we take the following particulars: Equal weights of carbon sulphide and of phosphorus, both as pure as possible, are put in a flask, and a little water added which floats on the top and prevents the sulphide from turning to vapor and from taking fire. The whole having been placed in some situation where it will not be disturbed, the sulphur of the sulphides combines with the phosphorus and releases the carbon, which falls to the bottom and assumes a crystalline form. This result takes place slowly, and not till after the lapse of six months was M. Gaunal able to obtain diamonds the size of a grain of millet-seed. As for the purity of these small diamonds it was proved by the strictest tests, and that not only by M. Gaunal but also by others. The experiment was repeated several times in the course of many years by M. Gaunal, and always with the same result. The artificial diamonds consist of pure carbon in dodecahedral crystals, and they scratch steel like the natural diamond.
Protection of Iron Surfaces from Rust.—We have already briefly described Professor Barff's method of rendering the surface of iron unoxidizable, yet, by way of introducing some remarks on the results of the process published in the "Lancet," we may repeat that it consists merely in subjecting the iron to the action of superheated steam—steam having a temperature of 1500° Fahr. This steam is generated in an upright boiler, and is then conducted through