REVIEWS AND BOOK NOTICES. 35 
tionable data to other explorers. We have not space now to nite 
from this part of the report except so far as relates to the age of 
the mound at Silver Spring, a large shell heap of from two to 
twenty feet in height and said to cover an area of about twenty 
acres. This heap is made up almost entirely of the small fresh 
water shells of the genera Ampullaria and Paludina, and, as Prof. 
Wyman remarks, it seems incredible to conceive that such vast 
numbers of small shells could have been brought together by 
man from the waters about, and the immense size of the mound 
must be regarded as. the work of many years and probably of 
centuries. 
“« There is to be seen at Silver Spring a grove of live oaks, a 
few survivors of a race of giants once common in the forests 
near the dct and to which my attention was called by my 
friend G. A. Peabody, Esq. Six of these at five feet from the 
ground ae as follows: one thirteen feet, three fifteen, one 
ninetdck! and one = cee twenty-six and offense feet i 
from one-half of the trunk, all that now remains, but agrees 
closely with measurements made several years before by Mr. 
Peabody, when the trunk was still whole. These trees are not on 
the highest part of the mound, but on the slope farthest from the 
water. Excavations made beneath the largest of them showed 
that the tree was of more recent origin than the mound itself. If 
at the beginning of the second century of the life of the live oak 
there are twelve rings at least to the inch, then the above men- 
tioned tree, having a a semidiameter of fifty inches, would have an 
age of not less than six hundred years, and was near the beginning 
of the second century of its existence at the landing of Columbus. 
On the same basis of calculation, the least age of the mounds near 
Blue Spring, and at Old Town, would be about four hundred years. 
Though these estimates are to be regarded only as approximations 
to the truth, they, without doubt, carry back the origin of the 
RRE be ond the reach of history or tradition, and certainly 
ne or two centuries before the discovery of America. hough 
they cannot be more recent than the trees growing upon them, 
y have been, and probably were, finished long “es ih 
life of the trees above mentioned began 
Revision or THE AMERICAN OR Tyrant FiycatcHers.*— This 
revision of the Myiurchi is based upon all the SR material 
- *Stndies of the Tyrannidæ.— Part I. Revision of the species - E By ; 
Elliott Coues. Proc. ae Nat. Sci. Phila. e pp. 56-81. — > 
