Origin of Flint. 169 



fossils of that horizon, sometimes the form filled with finely crystallized 

 quartz, but generally taking the ordinary siliceous texture of the flint. 



I have observed that this formation extends from the southern part 

 of Knox county south for more than an hundred miles, and where 

 borings have been m"de for salt or oil, it is found to maintain a 

 generally uniform thickness of four feet. From west to south, I have 

 traced it on the surface about tliirty miles. The dip, south and east, 

 conforms to the ordinary strata of rock and coal. 



How far this formation extends in either direction, beyond where I 

 have traced it, I do not know, and only know that here is an extended 

 field of siliceous matter, which was iu some way deposited of nearly 

 uniform thickness, and encasing numerous specimens of carboniferous 

 fossils, with seams of coal laying above and below it. Below this 

 main stratum of flint is iron ore, and fossilifei'ous limestone, and 

 lower still, in parts of Licking and Muskingum counties, a white sand 

 rock, locally called glass stone, that has for a long time been used for 

 making glass in Zanesville. 



The ordinar}' theory for the origin of such siliceous deposts, 

 I believe, has been thermal springs, or the shields of diatomacese. 

 But no indications of conical foi-mations exi>ting here, giving evi- 

 dence of having been vents through which heated siliceous waters 

 have flown, such as are always found where this phenomenon has 

 existed, and the absence of any appearance of disturbance in the 

 luiderlying strata, I think, forbids the acceptance of the thermal spring 

 theory, and requires us to attribute to some other cause the appearance 

 attributed to a high temperature present when it originated. 



The other theory is, that flmt is made up of the microscopic, siliceous 

 shields of the diatoms, which are generally regarded as plants, although 

 Ehrenberg refers them to animalcules. These diatoms, Dana says, 

 grow so abundantly in some seas, that they are now producing large, 

 .-siliceous accumulations. Professor Newbery, in a recent series of 

 notes on the history of plant life on the globe, contrasts the abund- 

 ance of diatoms during and since the tertiary period with their pre- 

 vious rarity, and suggests as an explanation, the ready solubility of 

 the silica of diatom shields, and thinks " the early diatomaceous beds 

 may have been destroyed and obscured from this cause, and the large 

 amount of siliceous matter which appears in sedimentary rocks, as 

 chert, buhr-stone, silico-calcareous beds, etc., in the Western States 

 especially, may be largely of diatomaceous origin ; and the material 

 being plainly indigenous in the deposits, there are no such evidences 

 as would allow", in the cases referred to, of the explanation of thermal 

 spring action.'' Although the flint of which w^e speak is of carbonifer- 



