Scientific American Supplement, No. 455, September 20, 1884 | Page 2

on the temperature of the earth, as shown by deep mines, were presented by Messrs. Hamilton Smith, Jr., and Edward B Dorsey. Mr. Smith said that the temperature of the earth varies very greatly at different localities and in different geological formations. There are decided exceptions to the general law that the temperature increased with the depth. At the New Almaden quicksilver mine, in California, at a depth of about 600 feet the temperature was very high--some 115 degrees; but in the deepest part of the same mine, 1,800 feet below the surface and 500 feet below sea level, the temperature is very pleasant, probably less than 80 degrees. At the Eureka mines, in California, the air 1,200 feet below the surface appears nearly as cool as 100 feet below the surface. The normal temperature of the earth at a depth of 50 or 60 feet is probably near the mean annual temperature of the air at the particular place. At the Comstock mines, some years since, the miners could remain but a few moments at a time, on account of the heat. Ice water was given them as an experiment; it produced no ill effects, but the men worked to much better advantage; and since that time, ice water is furnished in all these mines, and drunk with apparently no bad results.
Mr. E.B. Dorsey said that the mines on the Comstock vein, Nevada, were exceptionally hot. At depths of from 1,500 to 2,000 feet, the thermometer placed in a freshly drilled hole will show 130 degrees. Very large bodies of water have run for years at 155 degrees, and smaller bodies at 170 degrees. The temperature of the air is kept down to 110 degrees by forcing in fresh air cooled over ice.
Captain Wheeler, U.S. Engineers, estimated the heat extracted annually from the Comstock by means of the water pumped out and cold air forced in, as equal to that generated by the combustion of 55,560 tons of anthracite coal or 97,700 cords of wood. Observations were then given upon temperature at every 100 feet in the Forman shaft of the Overman mine, running from 53 degrees at a depth of 100 feet to 121.2 degrees at a depth of 2,300 feet. The temperature increased:
100 to 1,000 feet deep, increase 1 degree in 29 feet. 100 to 1,800 feet deep, increase 1 degree in 30.5 feet. 100 to 2,300 feet deep, increase 1 degree in 32.3 feet.
A table was presented giving the temperatures of a large number of deep mines, tunnels, and artesian wells. The two coolest mines or tunnels are in limestone, namely, Chanarcillo mines and Mont Cenis tunnel; and the two hottest are in trachyte and the "coal measures," namely, the Comstock mines in trachyte and the South Balgray in the "coal measures." Mr. Dorsey considered that experience showed that limestone was the coolest formation.
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GALLISIN, AN UNFERMENTABLE SUBSTANCE IN STARCH SUGAR.
C. Schmitt and A. Coblenzl have made a careful investigation of the unfermentable substances found in commercial starch sugars, and have succeeded in isolating a definite compound, to which they give the name gallisin. The method of separation and purification which they made use of is as follows: 5 kilogrammes of commercial starch sugar were allowed to ferment. At a temperature of 18-20° C. and with a solution containing 20 per cent. the fermentation was complete in five to six days. It was filtered; the perfectly clear, almost colorless, liquid evaporated as far as possible on the water-bath, and the sirup while still warm brought into a good-sized flask. The sirup was then well shaken with a large excess of absolute alcohol, when it became viscous, but did not mix with the alcohol. The latter was poured off, replaced by fresh alcohol, and again shaken. When this shaking with alcohol has been repeated several times, the sirup is finally changed to a yellowish-gray mass. This is now brought into a large mortar, and rubbed up under a mixture of alcohol and ether. After some time the whole mass is transformed into a gray powder. It is quickly filtered off with the aid of an aspirator, washed with alcohol and then with ether, and brought under a desiccator with concentrated sulphuric acid. In order to purify the substance, it is dissolved in water and treated with bone-black. The solution is then evaporated to a sirup, and this poured into a mixture of equal parts of anhydrous alcohol and ether. In this way the new compound is obtained as a very fine, pure white powder which rapidly settles. It has much the appearance of starch. Under the microscope it is perfectly amorphous. In the air it deliquesces much more rapidly than ignited calcium chloride.
Treated with dilute mineral acids or oxalic acid on the water-bath gallisin