THE LOWER COAL MEASURES. 291 
FLEVRE LX 
STRUCTURE OF CAMBRIDGE'-COAL SEAM 
AT NORRIS' MINE 
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showing good evaporative power, and making but little troublesome 
clinker. The coal is cleaned by screens that are 1} inches between the 
bars. These screens remove from one-third to one-half of what is sent 
out in the fbank-cars. The railroads are coming to use more of the 
smaller grades of coal, one-sixth of nut coal being taken with the lump 
coal in many contracts, but the slack and smaller grades of coal are for 
the most part entirely lost. 
The bank-cars are brought out by a wire cable, the Norris mine 
being one of the first in the State to succeed with this apparatus. The 
main entry is worked “quartering,” for the sake of making a straight 
course for{the cable. At 110 yards from the bank mouth a “horse- 
“back” of Mahoning sandstone\was struck. The coal was cut down to 
the slate parting. The entry was pushed forward through the rock for 
125 yards, without finding steady coal, and the question was raised 
whether the advance was. not being! made along the axis of the sand- 
stone trough. The coal will accordingly be attacked from other direc- 
tions. Clay veins come in to complicate the mining, and reduce the 
quality of the coal. Three of them occur within 60 or 70 yards on the 
west side of the trouble. ‘“‘Slickensides” is common in the coal, and 
reduces the strength of the pillars. One-third of the whole seam is 
left in pillars, and these latter are hard to win, and are quite largely 
lost. 
The composition of the coal from this part of the ‘mine is some- 
what below the standard, but it is believed that there is a large body of 
excellent coal tributary to this mine, and that its last days, which are 
very far away, will thus prove to be,its;best days. 
Analysis of the output shows the following results: 
