22,2, GEOLOGY OF OHIO. 
are liable to fire-damp, and require special care in ventilation, in order 
to be worked in safety. But from the first, they have been in the hands 
of competent and care taking men, and thus destructive accidents have 
been avoided. The system of ventilation in operation is excellent, and 
a full current is kept up to the working faces day and night. The 
entries and working faces are traversed every morning by an inspector 
before a miner is allowed to descend. The Market Street Shaft is 
counted, in all its management, as one of the best ordered mines of the 
State. It has been under the charge of William Smurthwaite for 20 
years, to whom the Survey is indebted for many of the details already 
given. 
The coal seam below the Shaft coal has always been found to 
abound in gas. Whenever it has been struck, a strong current has 
been found to issue from it. In some cases the supply has been utilized. 
THE NeEpso FIELD. 
Some new explorations have been made in the valley of Yellow 
Creek, in Springfield township, near Nebo, where the entrance of a line 
of railroad has led to quite careful examination so far as the coals are 
concerned. ‘The order of the strata at this point is clear and intel- 
ligible. The following section was obtained there: 
13. Crinoidal limestone, not seen, but found in adjacent hills. 
Tnterval scccascch usaeceecceeelescsecenes see oseecenae cocuisce ooaics aemececaenenes 30 to 50 feet. 
12. Second red clay band. 
11. Interval—chiefly blue and black shales with occasional 
Sandstone ledges: Aiet sedccssccinecececcecettecestoneecaessnceees 229 
10. Brush Creek coal—Groff Vein, No. 7 .............0..00.essesseeeoees 34 
Fire-Claye jc tikc. ssduseet eeccetecdnee ec seacse sesame cee oe eee 2 
9. Brush Creeks limestomey.c.secg-cccce sno cateooe coeteceeteeme tere cones 2 
8. Mahoning sandstone and sandy shales..................00+seeeseees 34 
7. Upper Freeport limestone, massive and brecciated............ 1-4 
6. Upper Freeport or Bolivar clay—white, red and blue......... 6 
Hae Sales). seca sccleeeccetises ceases terse aces eticesoslssssentsle cecvesiineececieecece 9 
A SE WAKO FS RopoKeny LW ay OLE? IOIREXE) DOTA dcc000 6600900000 670000000000000000000000000 18 
Bee BHAIES cs. secvscesegavonse concen seeeen samee cee eocoe tees cen occu otesceeemorcentt: 4 
OY, Ion erp IN ReXey oXeyeLy @Le JaKOV=C2F © (HOE b556065 060600000 6000G006000060060000000000 3 
1. Shales with calcareous NOdUIES .............cccerseccecsscscecececeees 6 
The section is continued downwards until both of the Kittanning 
coals, the Strip Vein and the Creek Vein, of the Hammondsville region, 
are struck. Several borings have been made, and more are going for- 
ward. One of these borings in progress at this date, made under direc” 
