General Science. 
189 
IV. GENERAL SCIENCE. 
44. Crystallisation of Water in Regular Rhomboids.— On 
the 3d of January the late Dr Clarke observed at Cam- 
bridge regular crystals of ice, many of which were more than 
an inch long. He exhibited them to several members of the 
University, and frequently in their presence measured the 
angles of the rhombic crystals, with the goniometer of Caran- 
geau, which he found to be 120° and 60°. After a thaw took 
place, the crystals preserved in melting the same inclination of 
their planes. The hexaedral prism of ice, therefore, which we 
have described in a former volume (Vol. II. p. 80.), as found 
in the subterranean glacier of Fondeurle, was a secondary form 
of the crystal. The above very interesting results confirm the 
anticipation of Dr Brewster, who, from the optical structure 
of Ice, referred it to the rhomboidal or pyramidal systems of 
Professor Mohs A full account of Dr Clarke’s observations 
will be found in the Memoirs of the Cambridge Philosophical 
Society^ voL i. part ii. p. 209^ 
45. Oil for Watch and Clock Work. — Good oil has long been 
a desideratum among watchmakers. Colonel Beaufoy remarks, 
that if olive oil be exposed to the rays of the sun for a consider- 
able length of time, it becomes colourless, limpid, free from mu- 
cilage, and not easily congealable. He exposed two eight-ounce 
phials, nearly filled with this oil, to the solar beams for one 
or two years, and found this effect produced. The bottles 
should be opened occasionally to allow the gas to escape, or the 
cork may be taken out. — The following process by Chevreul has 
been recommended for freeing oil for watch- work from all acid 
and mucilage. Put into a matrass or glass-flask, a portion of 
any fine oil, with seven or eight times its weight of alcohol, and 
heat the mixture almost to boiling, decant the clear upper stra- 
tum of fluid, and suffer it to cool ; a solid portion of fatty mat- 
ter separates, which is to be removed, and then the alcoholic so- 
lution evaporated in a retort or basin, until reduced to one-fifth 
its bulk. The elaine or fluid part of the oil will be deposited* 
It should be colourless and tasteless, almost free from smell. 
See Wernerian Memoirs^ vol. iii, p. 348. 
