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 CZ. soltaria 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 BING ule upper, or Sandusky, 
limestone having been entirely removed. 
On Kelly’s Island the limestone has been extensively quarried for 
