24:2 PROCEEDINGS OF SOCIETIES. 
Mr. D. Faxon, in Randolph, Mass., found under the following 
conditions :-— 
The surface of the country is generally undulating. There is 
slight depression, with a level tract in the centre, nearly circular, 
of about one hundred feet diameter, apparently like any ordinary 
New England meadow, flooded with water: but, on walking ono 
to it, it is found, unlike flooded meadow lands, to be not soft and 
miry, but nearly as firm and hard as the surrounding dry land. 
The surface is covered with grasses and turf two to three inches 
thick. Immediately below that is found the material exhibited, 
which has in one spot been excavated to the depth of ten feet 
without finding the bottom of it. It contains vegetable matter, 
afew fibres, to the amount of five or ten per cent.; the remainder 
is entirely organic, nearly all whole or broken frustules of 
diatoms, with some spicules of sponges. Not one particle of sand 
or other inorganic matter has been discovered after the strictest 
search with the microscope. 
The diatoms as yet have presented no species of particular 
interest. The genus Himantidiwm is most abundant; next, Pinnu- 
laria and Stauroneis. No attempt has been made to make any 
list of species found, as all are common in thousands of sub-peat de- 
posits in New England. It would be a matter of interest to know 
if the species are the same at different depths from the surface ; 
but no opportunity has yet been afforded for that, nor is it 
known from what depth the specimen examined was taken. 
Under what conditions could this enormous accumulation of 
diatoms have been deposited? An examination of land in the 
immediate vicinity has given the clue to a probable explanation. 
As already stated, the locality is a slight depression from the 
general surface around. There is a very small stream of water 
running into and through it. The outlet is through a ridge of 
drift gravel, and has been artificially deepened some five feet since 
the settlement of the country. Before this lowering of the 
outlet, the place must have been a pond, with some four to five 
feet of water above the present surface. The small stream 
running into it comes from some twenty or thirty acres of 
meadow, from a hundred yards to a quarter of a mile distant, and 
a few feet (less than ten apparently) higher level. Now the 
pond, when it existed, was too deep for the growth of peat-form- 
ing plants, and not favorable for the growth of diatoms in any 
large quantity. But the meadows above were, particularly before 
the cultivation of the country and the introduction of artificial 
drainage, most favorable for the growth of diatoms. The sluggish 
stream draining the meadows would have force enough, especially 
in floods, to wash out the diatoms, and not enough to move sand: 
neither could the meadows supply sand. When the diatoms 
reached the pond they would of course settle to the bottom ; for 
the mass of water in the pond being so great in proportion to the 
supply, there would be no perceptible current in it. In fact, 
it was a perfect natural trap for the diatoms, in principle exactly 
