58 HISTORY OF OHIO. 



pact masses, whose fracture is dull, splintery and sometimes 

 though, rarely conchoidal. It is opaque, at the edges; its 

 more common color is bluish or grey; it is seldom a pure car- 

 .bonate, but contains from two, to ten per cent, of silex. Some 

 of these limestones, are so impure, that they melt, rather than 

 burn into lime. Our limestone is of a recent formation, gen- 

 erally, and may be called, shell limestone. It is either found 

 in hills, with rounded summits, or under a level country. Its 

 strata are often thin, lying between strata of clay slate and 

 is composed almost wholly of sea shells. This limestone of- 

 ten presents fissures and rents, holes and cave?. 



In Kentucky, are caves of vast extent, and one of them, 

 has been explored twenty-one miles, under ground, called the 

 mammoth cave, in the vicinity of Green river. We have but 

 a few caverns, in our limestone region, and they are of no 

 great extent. 



In Highland county, are some caverns, near the Sinking 

 spring, and a few sharks' teeth were found in it, several 

 years since. The most valuable bed of limestone, now known 

 to exist, in this state, is situated five miles above Columbus, 

 on the main branch of the Scioto river, the property of Mr. 

 John McCoy. Large blocks are constantly taken from it, of 

 any desirable size, for pillars, and for fronts of houses. It is 

 a durable and beautiful building stone, and bears a tolerable 

 good polish. In McCoy's marble quarry is stone sufficient, to 

 last many centuries, for the Scioto country. 



Our limestone, furnishe an excellent lime, for building. 

 Its calicination is now effected by wood, but the heat should 

 not be great. 



Count Rumford, has invented an oven for burning lime. It 

 is a high cylinder, with the hearth at the side, and at some 

 distance above the base. The fire burns, with a reflected, or 

 inverted flame. The lime is taken out at the bottom, while 

 fresh additions of limestone are made at the top, so as to keep 

 the oven constantly heated. Limestone, either moistened or 

 just dug, calcines easiest. If dry, it should be moistened whea 

 put into the kiln. 



