STPAGENGHOLOG Isa 91 
raphy varies from flat to sharply rolling, the latter a product of glacial 
action. Two moraines cross the county from east to west; one of these 
lies in the southern part, the other near the middle. The latter seems to 
_ be the more conspicuous. Two principal streams, the St. Marys river and 
the headwaters of the Wabash, cross the county. These and _ their 
branches have broken the erstwhile flat portions of the county. 
Underground Features.—The succession and thickness of strata below 
drainage are shown in the following record of a well drilled at Celina :! 
Feet. 
IDNR H ES Ree Go. org bro DTS GEN Ge ONG OR CES RTECS EE Ee ae ee 70 
( Yellow 20 ft. ) 
¢ ; | White 65 ft. | 
Niagara limestone....... 1 Drath © he ' 135 
| Various shades 41 ft. J 
IN avaraeeShale Shsencsresicrssn2. SNS ent Senses ois A asus eles ais 15) 
@lintonaslinvestoneaecc was w een este ee eles ke we oa ches 43 
Mic Chintages Waleska ren ere tate cn emeine tsar Ome Sheetal ete ala 20 
Cincimmnatvios (ELIdSonmEOVeT) sislialesirrs) famines eres ote 480 
Witicagsh ales het ocmaisci tl eel ee teetry oka hk ed IIR SF Sis Stan 310 
PHReEntonesimMestonem atacrscaitas atte Weert Belle emotes 1,110 
Bottoms Olgawiell sia taesrst te scceare o eos sic tReet ene oases 1,168 
This makes the Trenton 235 feet below tide; near St. Henry, in the 
southern part of the county, the same formation is found at 205 feet 
(approximately) below tide. Examination of a large number of wells in 
various parts of the county shows the Trenton lying at about 1,090 to 
1,200 feet. The changes are gradual, indicating the absence of an arch, 
at any rate of a conspicuous one. 
Thus far the deeper pays reported in Wood and adjacent counties 
have not been reported in the county under consideration. The oil is 
commonly found at depths in the Trenton not exceeding 25 feet. ‘The rock 
is hard and fine, so that the wells usually make little promise until aftet 
having been shot. 
One of the striking geological features of the county is the pre- 
glacial channel already mentioned in connection with Auglaize and Shelby 
counties. It enters Mercer by two branches; one from the east runs west 
through the reservoir, the other from the southeast extends northwest 
through Franklin township. The two unite in the reservoir a short dis- 
tance east of Celina, and extend northwest past Rockford and then 
slightly south of west into Indiana, where it has been traced through 
Adams, Jay, Blackford and into Grant county. This old channel has 
been the most serious obstacle that the driller has had to contend with 
in those counties. 
Size and Duration of the Wells.—But little needs to be said on this 
subject, in view of what has already been given. Perhaps the largest 
well that has been drilled in this county was on the Murlin farm, section 
1Geol. Sur. of Ohio, Vel. VI, p. 259. 
