458 Institute of France. 
potash, and one end of it is welded together: in the other is in- 
serted a smaller tube perfectly air-tight, and destined to collect 
and retain the potassium. The apparatus thus adjusted, the 
wide tube is placed in a furnace, smith’s forge, or any powerful 
fire, when the potassium is sublimed, rises into the small tube, 
and is there collected pure and fit for use. ‘ 
Dr. Kidd communicated to the Society a short paper on the 
Formation of Nitre on the Walls of the Laboratory in Oxford. 
The walls are composed of a calcareous stone containing some 
shells, and the nitre forms on its surface in the greatest quan- 
tities where the walls are below the surface of the ground. It 
appears that the atmosphere assists its formation, as Dr. K, 
placed a glass over a part of the wall which yielded the nitre in 
greatest abundance, when the rapidity of its production was 
greatly impaired. The nitre produced is tolerably pure. 
Sir Everard Home, Bart. read a paper containing a deserip- 
tion of some fossil bones found in Dorsetshire, and new in Mr. 
Bullock’s museum. 
Sir E. has examined these fossil bones with great attention, 
but without being able perfectly to satisfy himself to what par- 
ticular species of animal they have belonged. The teeth he at 
first conjectured might be these of the crocodile, but on more 
mature examination he discovered that they could not possibly 
belong to that animal; the same uncertainty exists respecting 
the jaws and skull, which he determined not to be those of the 
shark genus. The non-existence of the elephant, hippopotamus, 
&c. in this country be considered as no argument why some of 
the bones found in Dorsetshire should not have belonged to 
those animals; but the depressions which the bones have ex- 
perienced, rendered it impossible for him to say positively to 
what species of animal they had belonged. Sir E.’s paper was 
illustrated by drawings of the different fossil bones alluded to. 
“PROCEEDINGS OF THE FRENCH INSTITUTE FOR THE YEAR 1813, 
BY M. CUVIER. 
[Continued from p. 311.] 
In our analysis for 1811, it has been seen how by accelerating 
evaporation in vacuo, and by thie presence of a strongly ab- 
sorbent body, Mr. Leslie of Edinburgh succeeded in freezing 
water at all times of the year. An apparatus which he subse-~ 
quently invented has been exhibited to the Class by M. Pictet; 
and our colleague M. Gay-Lussac, in repeating the experiment, 
recalled a well-known fact connected with the same subject, 
namely, that cold is produced in certain machines from which 
we 
