634 GEOLOGY OF OHIO. 
The specimens sent to the museum are of an attractive gray color 
and are highly fossiliferous. Some fossils have apparently been entirely 
removed at some period and their places subsequently supplied with a 
clear crystalline calcite, and some of the fossil forms are therefore 
strikingly apparent upon polishing the surface of the stone. 
Under the microscope the stone is found to consist of a coat 
ageregate of fossil fragments, among which here and there the rhombo- 
hedral crystals of dolomite are developed in much perfection. The 
number of these rhombohedral crystals is, as usual, proportionate to the 
amount of magnesia in the rock, which in this case is about 16 per cent. 
The limestone industry in and about Sandusky is one of the most 
extensive in the state. This is partly due to the abundant and excellent 
supply of building stone furnished by the Corniferous strata of this 
region, and partly to the facilities for transportation by water and by rail. 
The city of Sandusky is tounded upon a ledge of limestone, and excava- 
tion of any kind necessitates quarrying operations. In early days the 
stone thus extracted was the cheapest building material accessible, and 
came to be used very extensively. Asa result the use of stone is more 
general there than in any other Ohio town. 
At Sandusky the upper layers of the Corniferous formation are 
composed of a blue limestone of a thickness from 20 to 25 feet. This is 
underlaid by the white Sandusky limestone, which is found in thicker 
courses, cuts easier, and is capable of making a better lime; but at 
Sandusky this stratum, which is also from 20 to 25 feet in thickness, 
lies beneath the level of the lake, and is not readily accessible. The 
dip of the strata is, however, away from the water, and consequently 
this layer of white limestone is brought to the surface at Marblehead 
and on Kelley’s island. 
The largest quarries are situated at these points. Sandusky itself, 
owing to the circumstances mentioned, possesses quite a large number of 
quarries, and the city itself constitutes in fact a great limestone quarry 
covered with but a very shallow layer of soil or earth. These city 
quarries have been worked very largely for home and foreign supyly, 
not less than 12 acres having been excavated to a depth of 8 feet. The 
Sandusky blue limestone is found in layers of convenient thickness, and 
the range work furnished by it presents an attractive appearance. ‘The 
courses vary between 4 and 10 inches in thickness, and the material is used 
largely for flaggings, although not very well adapted for this purpose. 
is laid in slabs from 4 to 8 feet square, which are not very smooth or 
