190 Dr. Marcet on the specific gravity and temperature 
general law, or to explain the phenomena by particular theo- 
ries.* Why, for instance, two neighbouring and almost 
contiguous portions of the ocean, placed nearly alike in regard 
to solar influence, should differ so widely in the temperature 
of their waters, the warmer strata being, in one case, found 
lying above the colder, while in the other that order is re- 
versed, appears perfectly unaccountable. Whether, also, this 
singular circumstance may lead to inferences bearing upon 
the question now at issue respecting a north-west passage, I 
shall not presume to decide. But I may be allowed to indulge 
a hope, that the facts collected in this paper, may assist fu- 
ture inquirers in forming more accurate views of those grand 
phenomena of nature, in which the navigation of certain seas, 
the vicissitudes of seasons, and the geological history of the 
globe are so essentially concerned ; or that they may at least 
be the means of inducing other and abler observers to turn 
their attention to this interesting subject. 
• Count Rumford, in one of his Philosophical Essays (Vol. II. Essay VII.), in 
endeavouring to trace this class of natural phenomena to final causes, was led to some 
speculations and generalizations on the comparative temperature of the seas, and of 
large lakes, at their surface and at different depths, and on the relation which these 
temperatures bear to climate and to human comfort, which, however hypothetical, 
possess considerable plausibility and interest. Count Rum ford’s general idea was 
that the uniform temperature of large lakes at great depths, which De Saussure 
found in the Swiss lakes to be constantly between 41 0 and 42 0 , was naturally ex- 
plained from the circumstance since discovered, of water possessing its greatest den- 
sity at about that temperature ; and he conceived that the object of this law of nature 
was to preserve in winter a store of warmth at the bottom of these lakes, by which 
their freezing was retarded at the surface, and altogether prevented at a great depth, 
thus affording a check to the effects of severe winters. With regard to salt water, 
however, he took it for granted that the law which fixes the greatest density at about 
40°, did not prevail; but that, on the contrary, sea water being denser in proportion 
is at is colder, the coldest strata must occupy the bottom of the sea, while the warmest 
arising to the surface, serve to moderate the effects of the Arctic cold. He then 
