UNION COUNTY. - 327 



Quercus tinctoria — Black Oak Bart. 



Tilia Americana — Basswood J L. 



Cornus fiorida — Dogwood L. 



Carya alba — Shag-bark Hickory Nutt. 



Carya porcina — Pig Hickory , Nutt. 



Platanus occidentalis — Sycamore L. 



iEsculus glabra — Buckeye Willd. 



Zanthoxylum Americanum — Prickly Ash Mill. 



Acer rubrum — Soft Maple L. 



Carpinus Americana — Blue Beech Michx. 



Quercus alba — White Oak L. 



Quercus macrocarpa — Burr Oak L. 



Ulmus fulva— Slippery Elm Michx. 



Fraxinus Americana — White Ash L. 



Fraxinus sambucifolia — Black Ash Lam. 



Gleditschia triacanthos — Honey Locust L. 



Celtis occidentalis — Hackberry L. 



Crataegus coccinea — Thorn . L. 



Salix nigra— Black Willow Marsh. 



Juglans nigra — Black Walnut L. 



Quercus castanea — Chestnut-leaved Oak Willd. 



Prunus serotina — Black Cherry Ehr. 



Pyrus coronaria — Wild Apple L. 



Ostrya Virginica — Ironwood Willd. 



Populus monilifera — Cottonwood Ait. 



Asimina triloba — Pawpaw Ait. 



Populus tremuloides — Trembling Aspen Michx. 



Cercis Canadensis — Judas Tree L. 



Quercus palustris — Pin Oak DuBoi. 



GEOLOGICAL STRUCTURE. 



The rocks of the county embrace the following limestones, including, 

 also, the Oriskany sandstone : 



.Devonian. 



Hamilton, or 



Upper Corniferous, 



Lower Corniferous, 



Oriskany, J 



Waterlime Upper Silurian. 



ii 

 By the Hamilton is here meant the blue limestone which is quarried 

 at Delaware, and which is regarded by Dr. Newberry as partly Hamilton 

 and partly Corniferous. It has been mentioned frequently by the writer 

 in reporting on counties in north-western Ohio, under the designation 

 of Upper Corniferous, in order to keep it distinct from the underlying 

 limestone, which is plainly Corniferous. In the coloring of the county 



