( 146 ) 
On a DiATOMACEous Deposit in LevenWater, near Coniston. 
By Amos Beardsley, F.L.S., F.G.S., &c. 
(Read March 4th, 1857.) 
Leven Water is a mountain tarn, a large sheet of water 
embosomed in tlie rocks to the north of Coniston Old Man. 
When full it covers a surface of about eighty acres_, and is 
about twenty fathoms deep. The rocks surrounding this tarn 
are chiefly composed of hornstone_, porphyry, and trap. It is 
about 1300 feet above the sea-level. The mountains sur- 
rounding are for the most part on the north, north-east, and 
west sides. When visiting this water, in company with some 
friends, I observed the bottom of it to be entirely covered 
with a blackish pulverulent deposit, and from a careful 
examination on different sides of the lake, I found that this 
deposit extended all round, and though of various thickness, 
yet in every part it was some two or three feet thick, whilst 
in others I ascertained it to be six or eight feet. It appeared 
to be thickest in the vicinity of the rills or streams that, 
flowing down the mountain sides, empty themselves into the 
lake. Suspecting this deposit, from its appearance, to consist 
chiefly of diatom aceous remains, I brought a little of it home, 
and subjected it to the microscope, and was highly gratified 
to find that I was correct in my supposition. I have supplied 
various friends with portions, and all have been pleased with, 
the many forms it exhibits. It is not brought under the 
notice of the Society as at present having yielded any new 
species or varieties of diatoms ; stiU it appears to be interest- 
ing, as affording a good instance of how a deposit is now 
forming of considerable thickness, and which may throw 
some light upon the manner in which other and older deposits 
have been left. 
The Diatomacese here found have undoubtedly grown on 
the sides of the mountains around the lake, and been washed 
down by the rains, &c., by the rills and streams into the 
lake, where they have accumulated for ages. I am informed 
by Mr. Barratt, of Coniston, that the bank which is across 
the south end of the lake was made about twenty years ago 
to retain the water for the use of the copper-mines which 
are in the vicinity, but that two or three years ago the lake 
was " tapped twenty-one feet deeper, so that it can now be 
drawn off to a depth of forty feet. When I visited it the 
lake was low, and therefore close to the margin, and some 
feet above it, this deposit was exposed, which probably would 
not be noticed if the lake were fuller. 
