on the Maximum Density of Liquids. 51 
until it had receded an inch and three quarters, when the ship 
again rested on her pawls, where she was placed on the Saturday 
previous. 
It may be added that the liquor used in the presses at this time 
was found, upon analysis, to contain about 43 per cent. of alco- 
hol of the specific gravity of .825. Now it is well known that 
the rate of contraction of such a liquid, by the reduction of tem- 
perature which occurred in this case, at least at the ordinary 
pressure, is greater than that of iron. In order to satisfy myself 
of the correctness of this statement in the present instance, I 
took a two ounce bottle, to which a tube of about a foot in 
length, with a bore of one eighth of an inch, was attached, and 
filled the bottle and tube with the liquor employed in the press. 
The whole was then placed in a freezing mixture, and the tem- 
perature gradually reduced to 0° F.., supposing that to be the 
lowest degree to which it had been exposed in the cylinder. 
With the reduction of temperature, the liquor constantly descend- 
ed in the tube, as I had anticipated. 
What then was the cause of the outward movement of the 
ram, by which such an enormous force was exerted, as to raise 
the whole of this vessel and the cradle which supported it? 
The column of liquid was certainly increased in length by an 
inch and three quarters. If the liquid had remained of the same 
bulk, the apparent increase might be ascribed to the contraction 
of the iron. But this view seems to be inadmissible, for the con- 
traction of the iron would, under ordinary pressures at least, 
have been less than that of the Naud, as has been shown by re- 
peated experiments. 
The explanation which I would offer is, that the mixture of 
alcohol and water, under the enormous pressure to which it was 
subjected in the hydraulic press, reached its point of maximum 
density at a higher temperature than under the ordinary pressure. 
The liquor in the cylinder during the time above mentioned, was 
either congealed or was near the point of congelation, and thus 
increased in bulk. Hence the outward movement of the ram, 
and the raising of the ship. 
In the discussions which were had in regard to the present 
mode of graduating thermometers, I know it was suggested that 
the freezing point of water varies with the latitude; which, how- 
ever, was proved not to be the case. But Iam not aware that 
