Mac Fartane—Seiches in Lake Derravaragh, Co. Westmeath. 295 
common form of Volvox, the clusters or groups of cells, which form 
the families, being more or less lobated or constricted, and showing 
a decided but very gentle independent motion of an oscillatory 
character, giving the idea of the existence of cilia, although none 
could be discovered." 
Another somewhat phenomenal occurrence on the shore of 
Lake Derravaragh is seen in a small portion of a covert of Knock- 
body. During summer rains, or when the atmosphere is heavy 
with warm moisture, large volumes of steam, resembling smoke, 
issue from about the tree tops, but only in a circumscribed area of 
about an acre in extent. When seen under favourable circum- 
stances, this presents a very curious spectacle, as if large fires had 
been kindled under the trees; the dense steam, rising in volumes 
at times, again dying down, having every appearance of smoke. 
Local opinion is divided on this matter; the shaft of an old 
mine; fairies lighting fires; or a small mouth of Hades being the 
most favourite explanations. 
The cause, without doubt, is warm air condensing over a 
spring of very cold water situated in that particular part of the 
covert. 
A traveller in North America assures me that on many an 
occasion a similar spectacle was there hailed with great delight, 
manifesting, as it did, the presence of a cold spring. 
It is highly probable that seiches occur on many, perhaps on 
all, lakes; but that in the majority of cases the amplitudes are so 
slight that the occurrence escapes notice; this is greatly borne out 
by the fact that it was only dueto the careful watching of a batten, 
specially put up, that the seiches on Lake Derravaragh were ever 
noticed, although having, as far as at present known, an amplitude 
reaching 6 inches. 
Before concluding this Paper I should wish to mention a 
phenomenal rise and fall of the river Shannon which I observed 
subsequent to writing the preceding notes. 
I was fishing on the river about eight miles above Lough Derg, 
and happened to notice a stake, standing up from the bottom of 
the river, with its head showing about 3 inches above the water. 
A very short time afterwards my boatman drew my attention to 
‘See Quarterly Journal Microscopic Society, 1869, p. 197. 
