54 Dr. B. F. Harrison on Solution of Ice on Inland Waters. 
dundant heat to the superincumbent waters. My observations 
show that the basin of the lake is in much the same relation with 
the heat of summer that it would be if there were no water in it— 
that is, it receives about the same mean temperature; but in win- 
ter the case is widely different. The bottom of the lake is never 
cooled below 39°, and even this temperature is considerably lower 
than would be reached at an equal depth (25 feet) in the solid 
earth, where, if the authorities are correct, the temperature should 
not fall below 46° for our latitude. The lake in winter has as- 
similated itself to the solid earth in that it has attained its maxi- 
mum density and its surface is converted into solid ice; both the 
ice and the water in this condition are so slow conductors of 
heat that very little can escape into the atmosphere. Under these 
circumstances, the tendency to the equilibrium of heat in the 
earth will raise the temperature at the depth of 25 feet (the 
bottom of the lake) to its usual amount at that depth from the 
earth’s surface, and that too quite independent of any accumula- 
tion of summer heat. Thus we find another source of heat be- 
low the lake, which we may expect to augnient the temperature 
of the waters under the ice. It thus happens that the bottom o 
the lake attains the mean temperature of the atmosphere in the 
warm season, and that it always is maintained at a temperature 
20° above the mean of the coldest months. 
Water attains its maximum density at 39°-2 F., from which 
point it is said to expand by a change of temperature in either 
direction ; yet my observations appear to show that water in wi 
masses may be heated up to 42° without disturbing its equili 
rium. I have often found the temperature of 42° at the bottom 
of the lake (25 feet) when the surface was 33°, and 89° was found 
only 6 feet below the surface. A mass of water with its maxi 
mum density at a distance from its surface of only one-fourth 
part of its depth would doubtless have its equilibrium very easily 
disturbed by any agitation, as of the wind, and thus bring the 
warmer water of the bottom into contact with the ice at its sur- 
face. I do not claim that all the ice is dissolved in this manner, 
I only propose to show that, when the solution has commenced, 
natural laws bring into action an amount of reserved heat sufli- 
cient to finish the solution in a very short time. : 
When, on the approach of winter, the process of cooling com- 
mences it proceeds much more rapidly in the waters of the lake 
than in the earthy bed on which it rests ;—the heat escaping from 
the water by radiation, evaporation, conduction and convection, 
the colder water at the surface sinking and the warmer msing; 
until the water of the lake attains its greatest density, after 
which the surface water expands as it cools and soon freezes, 
producing a covering of ice which protects the water from agita- 
tion by the winds. The process of heating from below then 
