200 GEOLOGY OF OHIO. 



pendent in part upon the equable climate which they enjoy, and which 

 they owe to the broad expanse of water surrounding them. The summer 

 is longer upon the islands than upon the main land, and frosts are much 

 less likely, in spring and fall, to injure blossoms or prevent the ripening of 

 fruit. The mildness of the climate is also shown by the presence and 

 luxurious growth of many plants which belong to the flora of the south- 

 ern portions of the State. 



In the condition of nature, the islands were covered with a dense forest 

 and undergrowth, from which had accumulated an unusual thickness of 

 humus, and this has given them their extraordinary fertility. Another 

 peculiarity of the islands, depending probably both on the peculiarities 

 of the climate and the calcareous quality of the soil, is the vast numbers 

 of land-shells found upon them. Several species of Helix, which are 

 somewhat rare on the main land (H. solitaria and H. multilineata), occur 

 here in such abundance that the soil in some localities is whitened by 

 and largely composed of their shells. 



When first visited by the whites, the margins and many of the more 

 rocky portions of the islands were covered with a dense growth of red 

 cedar. This has been now entirely cut away, largely by plunderers, and 

 nought but the stumps remain to witness to the unusual size of the trees 

 which formerly flourished there. The primeval forest was, however, 

 composed, for the most part, of white oak, and this, when cut away (if the 

 area is not immediately placed under cultivation), is followed by a dense 

 growth of sumach, which attains here greater dimensions than I have 

 elsewhere seen ; and it is probable that, from the value of their bark in 

 tanning and their luxuriant growth, these trees might prove a crop 

 scarcely less remunerative than any now raised on the islands. The 

 lower and more level parts of the surface formerly sustained a very heavy 

 growth of maples and hickory, and here, as elsewhere, the first was thickly 

 interwoven by vines of the wild grape, which, by their size and luxuri- 

 ance, were prophetic of the success that has followed the introduction of 

 cultivated varieties. 



kelly's island. 



Geological Structure. — Kelly's Island and Middle Island are composed 

 entirely of Corniferous limestone, as they lie in the line of the belt of 

 outcrop of this formation which passes northward through Columbus, 

 Delaware, and Sandusky. Only the lower, or Columbus, division of the 

 Corniferous limestone is shown on these islands — the upper, or Sandusky, 

 limestone having been entirely removed. 



On Kelly's Island the limestone has been extensively quarried for 



