316 GEOLOGY OF OHIO. 



Tilia Americana — Basswood L. 



Populus monilifera — Cottonwood Ait. 



jEsculus glabra — Buckeye Willd. 



Quercus rnacrocarpa — Burr Oak Michx. 



Populus grandidentata — Large-toothed Aspen Michx. 



Prunus Americana — Plum Marsh. 



Acer rubrum — Swamp Maple L. 



Fraxinus sambucifolia — Black Ash Lam. 



Gymnocladus Canadensis — Kentucky Coffee Bean Lam. 



Prunus serotina — Black Cherry Ehr. 



Populus tremuloides — Trembling Aspen Micbx. 



Rhus glabra — Sumach L. 



Crataegus tomentosa — Black Thorn L. 



Populus balsamifera — Balm of Gilead L. 



Quercus palustris — Pin Oak DuEoi. 



Juglans cinerea — Butternut. [Seen only on the Van Wert ridge]... L. 



Asimina triloba — Pawpaw Dunal. 



GEOLOGICAL STEUCTUEE. 



The rocks of the county belong to the Upper Silurian. The upper 

 member of the Niagara, the equivalent of the Guelph of Canada, or of 

 the Racine limestone of the West, is the lowest in outcrop in the county. 

 It underlies a tract of uncertain limit in the south-western part of the 

 county, and is exposed in the St. Mary's River, at Willshire. Over this 

 lies the Waterlime, belonging to the Lower Helderberg. 



The former is a porous, magnesian limestone, of rather repulsive aspect, 

 its naturally light color being generally stained with iron- rust. In quar- 

 rying it shows a blue color. It lies in. thin beds of three to five inches, 

 occupying usually the protected and most retired points of outcrop, owing 

 to the rapidity with which it disintegrates under the forces of nature. 



The latter is, in Van Wert county, very similar in general appearance, 

 but it has different fossils, and is harder. It is less porous. It has a 

 drab color, but the color is lighter in Van Wert county, and in counties 

 further north, than it is in Allen and Hardin counties, where it is often 

 blue, or even becomes so bituminous as to be black and slaty. Its most 

 slaty character is seen in Wyandot county. In Van Wert county, and 

 also in Putnam, it is not slaty, or very rarely so, and shows very little 

 bituminous matter. It burns to a very white lime in the township of 

 Union, where there is a surface exposure, but in Washington township, 

 near Delphos, it is thinner bedded and more bituminous, the lime also 

 becoming darker. 



Niagara Limestone.— The only exposure of this stone known within the 

 county is at Willshire, in the bed of the St. Mary's River, and in a small 



