42 
In the year 1804, I made some experiments on Lough Ness in 
the north of Scotland, in company with my friend Simon Frazer, 
Esq. of Foyers ; to discover the temperature of the water at the bot- 
tom of that lake, and whether it had any impregnation of salt 
agreeable to the theory of Count Rumford. After dropping a ves- 
sel of half a gallon several times to the depth of 120 fathoms, 
we found the boat had gradually drifted a mile up the lake, though 
the day was rather calm, and what little wind there was was blowing 
downward. We could only account for this, by suposing a subequeous 
eddy to be produced by the waters of the surface being blown to- 
wards the lower end and returning by the bottom. 
Accordingly, on an examination of the bottom of the sea along 
the north eastern shores of Ireland, I found this order of arrange- 
ment to be nearly what occurs. 
From Howth, within Lambay and Rockabill, we have patches 
of rough ground, stones, shingles, and clay, to the Skerries Isles ; 
another patch of this kind is found north of Clogher head; one 
north of Dunany extending to Cooley point, the Helly hunter rock 
off the coast of Mourne, &c. Outside of these, we have a zone 
of clean ground and sandy bottom from the Wicklow banks by 
Howth head, outside of Lambay to St. John’s point, and thence to 
the Copeland. Such ground ‘is fit for trawling on, and therefore 
its limits are well ascertained. 
Beyond the sand, we have mud and ooze in the deep water until 
we approach the shores of the Isle of Man, where the sand and 
then rough ground again returns. The mud ground cannot be 
fished by the trawl: it is the resort of the cod and ling, which are 
taken by the hook and line, so that its extent is pretty well known 
to the fishermen. This mud ground however does not occupy the 
deep water generally ; but is confined to particular places. 
On the hypothesis that the bottom of the sea is a great bed of al- 
