ee 
1817.) New Patents. 413 
three inches in diameter at the height of half an inch above it, and 
covered the whole with a low receiver. On exhausting the air from 
this receiver till the gauge stood at two-tenths of an inch, the water 
in a very few minutes was converted intoa cake of ice. With the 
same powder, above an hour afterwards, |] repeated the experiment 
in the presence of one or two friends; and in the space of three 
minutes after the receiver was placed, a larger body of water began 
to congeal, and was quickly consolidated. 
It appears that such dried earth will absorb the 50th part of its 
weight of moisture before its absorbing power is diminished one 
half, and the 25th part of its weight before this power is reduced 
to one fourth. When completely saturated with humidity, it may 
hold near a fifth part of its whole weight. Since, therefore, the 
quantity of heat abstracted by the process of evaporation is adequate 
to the congelation of about eight times an equal weight of water, 
the dry pulverized green-stone or garden mould is capable of freez- 
ing more than the sixth part of its weight of water. To ensure 
success and expedition, however, I should prefer rather a larger 
proportion of the powder. The contents of two quart decanters, 
for instance, poured into a saucer of a foot diameter, might be em- 
ployed to freeze half or three quarters of a pound of water in a 
hemispherical cup of porous earthenware. This powder is capable 
of acting still, though with feebler effect. It should, therefore, 
after each process, be dried again, which will restore it completely 
to its former energy. Such partial drying will be quickly and easily 
performed ; and in hot countries the mere exposure of the powder 
for a while to the sun may be sufficient. Ice may, therefore, be 
procured in the tropical climates, and even at sea, with very little 
trouble, and no sort of risk or inconvenience. 
I mean to pursue this curious subject, and to institute immediately 
a series of experiments on different compound earths; and should 
the results prove interesting, I will not fail to transmit them te you. 
I an), dear Sir, very sincerely yours, 
Edinburgh, April 17, 1817. Jonn Lxsxr. 
ArrticLE XIV. 
New Patents. 
Joun We cn, of Preston, cotton-mill roller-maker; for an 
improvement in making rollers used in spinning wool, cotton, silk, 
flax, tow, or any other fibrous substances. Aug. 3, 1816. 
SamuEt Nock, of Fleet-street, London, gunmaker; for an 
improvement in the pans of locks of guns and fire-arms. Aug. 12, 
i8i6. 
Rozerr Trier, woollen-draper, Bristol; for an hussar garter 
with elastic springs and fastenings, and also elastic springs for pan- 
faloons and other articles. Aug. 14, 1816. 
