ably
not more than one in a hundred is really fine, therefore, as the worth
of a pearl depends on lustre and form, the greater number obtained from
this source are of slight value. Rev. Horace C. Hovey, however, is
credited with having found a pearl half an inch across in the shell of
a Unio ovatus, near Cincinnati, Ohio. Unio pearls have been sought
since the settlement of this country, and the narratives of early
voyagers abound with references to them. In an ancient catalogue1 of objects of natural history, made in 1749 by John Winthrop, F. R. S., the following items are mentioned:
" 30. Unripe pearls which in time would have become [31].
31. Bright pearls which are produced in the same shells [30].
32.
Some of the larger sea pearl shells which are often found in
deeper waters three times as large and bear larger pearls.
N.
B.—Almost all the lakes, ponds, and brooks contain a large fresh-water
clam which also bears pearls. The Indians say they have no pearls in
them at certain seasons, but at the season when they grow milky, the
pearls are digested in them, which causes their milkiness."
Dr.
Samuel P. Hildreth writes: " Some of the fresh-water shells produce
very fine pearls. I have one taken in the waters of the Muskingum, from
the shell known as the Unio nodosus of Barnes. It is a thick,
tuberculated shell, with the most rich and pearly nacre of any in the
western rivers. The specimen is perfect in form, being plano-convex on
one side and a full hemisphere on the opposite. It is nearly 1/2 inch
in diameter across the plane face, and 3/8 inch through the transverse
diameter, and of a very rich pearly lustre. Set in a gold watch-key and
surrounded by facets of jet, it makes a beautiful appearance and is by
far the largest and finest pearl I have ever seen. Several others have
been found, but none to be compared to this."1
The greatest find of these Unio pearls was in a mound in the Little Miami Valley explored by Prof. Frederick W. Put-
1 Am. J. Sci. I. Vol. 47, p. 284, Jan., 1845.
'Am. J. Sci. I., Vol. 25, p. 257, April, 1834. Ten Days in Ohio, from the Diary of a Naturalist.
