GEOLOGICAL SCALE AND STRUCTURE. 13 



ness of thirty feet in several sections. It is composed of very pure, 

 even-grained, sharp silicious sand. Other deposits of precisely the same 

 character are found in the two next higher limestones of the scale at 

 several points in the state. One of these deposits is interstratified with 

 the Waterlime in Scioto, Wood and Lucas counties, and others are im- 

 bedded in. the Corniferous limestones of central Ohio. The latter have 

 been referred to the Oriskany period, but, strictly speaking, this refer- 

 ence is inadmissible, inasmuch as normal Corniferous limestone with its 

 most characteristic fossils is found below as well as above the sandstone. 

 The subject will be further considered on a succeeding page. 



The Hillsboro sandstone is sometimes built up 'above all the beds of 

 the upper Niagara limestone, but again, it is, at times, interstratified 

 with the beds of the Guelph division. In the latter case it is itself fossil ■ 

 iferous, but when found alone it seems destitute of all traces of life. 

 These sandstones in the limestone formations suggest in their peculiari- 

 ties a common origin. They all contain many unworn and nearly perfect 

 crystals, and sometimes seem to be mainly composed of the same. Their 

 occurrence in outcrops becomes a matter of interest to us, now that we are 

 called to interpret the varied records of deep drillings throughout the 

 state. What would otherwise be altogether anomalous sections may be 

 rendered intelligible by the known presence of such elements in the 

 scale. 



The Salina Group. 



This group has appeared in all the recent tabular sections of the 

 rocks of the state, but in the light of facts obtained within the last four 

 years, it can no longer be counted a distinct or recognizable element in 

 the Ohio scale. Newberry gave it the place which it has held in the 

 column, and assigned to it a thickness- of forty feet. To jt he referred 

 the plaster beds of the Ottawa county peninsula, and certain impure 

 limestones of Put-in-Bay Island. He also recorded the disappearance of 

 what he counted the same stratum a few miles south of the lake shore, 

 in a shaly bed that rests immediately upon the Niagara limestone. 



The identifications are, however, incompatible. The limestones of 

 Put-in-Bay and the plaster beds of the peninsula do not directly overlie 

 the Niagara limestone as represented, but on the contrary are separated 

 from it by several hundred feet of the brown, even-bedded, sparingly f os- 

 siferous magnesian limestone that we call the Lower Helderberg lime- 

 stone or the Waterlime. In other words, the plaster beds of Gypsum are 

 buried in the middle-, or above the middle of this great sheet of limestone, 

 instead of being planted at its base. The reference of .this formation to 

 the Salina was rendered probable at the time from the fact that all the 

 gypsiferous formations of New York were then counted of Salina age. It 

 has since been proved, however, that gypsum is also contained in the 

 Waterlime of central New York, and it is in like situations that the Ohio 



