636 KANSAS CITY REVIEW OF SCIENCE. 
of perforator. The perforators used in the Mont Cenis and St. Gothard tunnels 
consisted of a series of chisels (not diamond pointed, as has sometimes been 
stated), driven with a quick, hammer-like action by compressed air, the machines 
for the production of which were actuated by turbines at the two ends of the 
galleries. This system was the one in use on the eastern, or Austrian, side of 
the Arlberg. The chisels cover a space of seven square meters, and make 
twenty to twenty-five holes at one time, each from one and a half to two meters 
deep. These are then filled with dynamite and the mine exploded. Every blast 
lengthens the drift by about one and a quarter meters. The perforators move for- 
ward on wheels, and the air, compressed to a pressure of five atmospheres, is 
supplied through flexible tubes. On the west side drills are employed of a diam- 
eter of seventy millimeters, to which, by means of a water pressure of from sixty 
to one hundred atmospheres, a rotary movment is communicated. Six or eight 
of these drills are as effective as twenty or twenty-five of the atmospheric perfor- 
ators, and the holes they make are so much wider that equal results are produced 
with lighter charges of dynamite. 
The greatest difficulty in Alpine tunneling consists less in quarrying out a 
passage than in gettmg rid of rubbish. After every blast the outcome of it, in 
the shape of loose material, must be removed before boring operations can be 
resumed; and when an atmosphere already close and impure is still further 
fouled by the smoke of an explosion, the labor of removal becomes dangerous as 
well as difficult. Fatal accidents sometimes happen. The leading miners in the 
Arlberg Tunnel, when engaged in this work, cover their mouths and nostrils 
with sponges which have been steeped in vinegar, an expedient which has been 
found singularly efficacious in neutralizing the bad effects of the poisonous air 
they are often compelled to breathe. The important part which the removal of 
rubbish plays in these undertakings is shown in the fact that of the time required 
for the making of the Arlberg Tunnel fully one-half was devoted to the carrying 
away of loose material. — N. Y. Herald. 
MINING IN COLORADO IN 1883. 
Following is a summary of the coal output of Colorado for the year 1883 : 
Tons. 
Mines near Erie and Canfield . 80,000 
Mines at Louisville ..... 103,321 
Mines at Langford ..... 45,500 
Mines near Golden 19,899 
Mines at Franceville . . - • 53,757 
Mines at Sedalia IjSoo 
Mines at Como . ,, 58,391 
Mines near Canon City . . . 272,103 
Mines near Trinidad .... 93,339 
Tons. 
Mines near El Moro .... 277,341 
Mines near Durango .... 12,000 
Mines at Rico 2,500 
Mines at Crested Butte . . . 75,983 
Mines at Castleton 14,846 
Other mines ........ 3,500 
Total product of Colorado . 1,114,040 
