Page:Popular Science Monthly Volume 14.djvu/137

Rh the latter substance in its general properties, that much of it is shipped yearly from Guiana and sold for that article, although in some respects it is greatly superior to gutta-percha. Like gutta-percha and India-rubber, this gum is obtained by making an incision in the bark of the tree, and allowing the sap to ooze out and either coagulate in a lump or flow slowly over a clay form so as to produce a "bottle" or any other pattern that may be desired. Balata is tasteless, gives out an agreeable odor on being warmed, is tough and leathery, is remarkably flexible, and far more elastic than gutta-percha. It can be softened and joined piece to piece indefinitely, at a temperature of about 120° Fahr., but requires a beat of 270° before it melts. It is completely soluble in benzol and bisulphide of carbon when cold. Turpentine dissolves it with the application of heat, while it is only partially soluble in anhydrous alcohol and ether. It becomes strongly electrified by friction, and is a better isolator of heat and electricity than gutta-percha. Caustic alkalies and concentrated hydrochloric acid do not attack it, but concentrated sulphuric and nitric acids do. A sort of artificial India-rubber, called "kerite," invented by A. G. Day, of this city, has recently been brought to. notice. It is prepared in the following way: About twenty-seven pounds of cotton-seed oil and thirty pounds of coal-tar are mixed together in a boiler, with sufficient heat and for a sufficient length of time to cause them to unite thoroughly. The temperature should be about 300° Fahr., and the time is from three to five hours. The mixture is then cooled to from 200° to 240° Fahr., and then linseed-oil (twenty-seven pounds) is added. When the latter has been thoroughly mixed with the other ingredients, twelve to sixteen pounds of sulphur is added gradually, the temperature meantime being steadily raised to about 275° or 300° Fahr. The heating is continued till the mass is vulcanized. When the vulcanization is complete, the compound is finished, and it may then be poured into moulds or pans and allowed to cool for use. The inventor has lately made some considerable improvements in his process of preparing ozokerite, but it would take too much space to detail them here.



American Association will next year hold its meetings at Saratoga, beginning on the last Wednesday of August. Prof. G. F. Barker, of Philadelphia, is the president.

September 6th, at Brussels, Ernest Quetelet, of the Brussels Royal Observatory, aged about fifty-three years. Deceased was the son of the late Prof. Adolphe Quetelet, the eminent statistician, who was the founder of the Brussels Observatory, and its director till his death in 1874.

the pterosaurian fossils hitherto discovered in the United States are from the Cretaceous. But in the American Journal of Science for September, Prof. O. C. Marsh describes a fossil specimen from the Upper Jurassic of Wyoming which proves the existence of that class of saurians in the formation just named. The specimen, which is in good preservation, is the distal portion of the right wing metacarpal, and indicates a small pterodactyl, having a spread of wings of four or five feet.

ingenious machine, invented by James H. Williams, was exhibited this fall at a Mechanics' Fair in Boston, viz., a machine capable of indicating, six to eight-times per minute, the superficial area of surfaces, however irregular, not exceeding twenty-five square feet. The machine can, for instance, compute in less than ten seconds the square contents of a circle without reference to mathematical rules. It is certain to find practical application in many departments of trade. It is specially of use to leather dealers and manufacturers for measuring exactly the superficial area of hides and skins.

the botanist, died at Cuenca, Bolivia, June 20th, aged forty-eight years. He first visited South America as a botanical collector in 1860, gathering new and useful species of plants, and during the ensuing eight years traversed Brazil, Peru, Ecuador, Bolivia, Colombia, Panama, and Costa Rica. He next visited the Philippine Islands, but in 1871 he again went to South America, never to return. He died in a hospital, in poverty, "worn out in the cause of science," says Nature. He introduced into European horticulture no less than 1,000 new varieties from across the Atlantic.

petroleum (kerosene), according to Prof. J. Lawrence Smith, should have the following characteristics: 1. The color should be white or light yellow, with a blue reflection; 2. The odor should be faint and not disagreeable; 3. The specific gravity, at 60° Fahr., ought not to be below 0.795 nor above 0.84; 4. When mixed with