610 GEOLOGY OF OHIO. 
The quarries in Butler county, from which are extracted the blue- 
limestone of the Cincinnati group, are situated at and near Hamilton. 
The character of the stone and the method of its occurrence are the same | 
as those of the other limestone obtained from this group. A quarry 
at Hamilton exhibits a section 40 feet thick, of which 18 feet is of stone 
distributed in layers of varying thickness throughout the whole section. 
The individual layers sre from 1 inch to 12 inches in thickness, and the 
heaviest layers are found at the bottom. 
The limestones of the Cincinnati group are all highly fossiliferous, 
and the number and variety of the forms found in them have given to 
them a geological celebrity. The quarrying operations are constantly 
bringing to light rare and interesting species, but the specimens which 
were collected and sent to the National Museum as typical contain a 
predominating number of fossils of the species Chaetetes (now Monticu- 
lipora), with the shells of brachiopods cemented together by limestone. 
When polished the stones appear very beautiful on account of the diversity 
and delicacy of these fossil forms, but owing to the presence of clay in the 
cementing material the polish is not uniform over the whole surface. 
This does not detract especially from the value of the stone for ornamental 
purposes, since the fossil forms which give the stone its beauty by 
receiving the highest polish are thereby brought into prominence. 
The fragments of fossils of which the stone so largely consists were 
apparently first washed together along with the clayey limestone and 
mud which forms the cement, and which fills the interiors of the fossil 
forms. This was apparently solidified into a vesicular rock, and the 
cavities were subsequently filled with clear crystalline calcite. The 
process of such formation is frequently seen in the Ohio limestone, some 
of which are porous, and are filled with cavities which are but partially 
filled with new crystalline product. Analyses were made of these lime- 
stones by Dr. Wormley for the Report on the Geological Survey of Ohio. (a) 
The Point Pleasant rock, which is considered to be the best for 
building purposes, was by him shown to have the following composition : 
‘Per cent. 
Siliceous; matter sac) Leeesas ohisssctede cose oe oMeiresmaesaea Cuca awtiomeeseetawseeecmenes 12.00 
Aluminasand iron: OX1d Obs .cscecessescscocecossecne este cas tees ee ee eee tees 7.00 
Calcium carbonate.......... siiead ob higdieie sale Gloss eenes ot tos meena cats eaeteseee enc ae 79.30 
IW IB ese F Ta 0 aie iA eeine cori oG so necscboabicoGoooboadodo0si60ddb0s6 060600500 100000000000 0.91 
Total ss. coe es ccise awa eee daaseepiclewesecesseosee cane osuceion caetes aasl eos eeecmeeete 99.21 
(a) Geology of Ohio, Vol. I, Part i, p. 375. 
