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

fire. A lamp having been enveloped with paper and lighted by a
current, the heat generated was sufficient to set fire to the paper, which
burnt out and caused the lamp to explode.
* * * * *

THE TEMPERATURE OF THE EARTH AS SHOWN BY DEEP
MINES.
At a recent meeting of the American Society of Civil Engineers,
observations 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.
* * * * *

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