Phosphorescence of Sub-resins. 189 
thirteen stars, as given by seven different observers ; and 
finds that, generally speaking, the greatest differences of re- 
sults have occurred in those stars whose proportionate re- 
frangibility, is the greatest and the least ; and that the differ- 
ences of results have been the least in Capella and those 
stars whose refrangibility is nearest to the mean. From nu- 
merous experiments Dr. F. concludes that the refractions of 
Capella appear to equal the mean refraction, and those of 
Lyra and Aldeburan the two extremes. 
29. On the effect of animal charcoal in preventing the putres 
faction of stagnunt water.—M. A. Chevalier, of Paris, hav- 
ing been consulted by a gentleman respecting the best method 
of preventing a pond in his garden from putrefying, recom- 
mended the employment of animal charcoal. The experi- 
ment was tried with perfect success. The small pond or 
basin was about 9 feet in diameter and 3 deep. The water 
proceeded from a spring; but towards autumn it became pu- 
trid, and exhaled a mephitic odour. On the 10th of August, 
1823, 45lbs of animal charcoal in powder were thrown into 
it, care being taken to spread it equally on the surface, where 
it at first floated ; but afterwards fell to the bottom. The 
effect of this was to remove all offensive smell from the wa- 
ter; and M. Chevalier upon examining a bottle of it, found 
that it had neither an offensive smell nor taste, though it had 
been out of the pond for § days. M. Chevalier observes 
that the animal charcoal which has been thus used in a pond 
might when taken out be used as a manure, as it gives out 
by slow degrees to vegetable bodies, the substances which it 
has absorbed. See the Journal de Pharmacie for 1824, p. 
73.—Dr. Brewster's Journal. 
30. On the phosphorescence of several sub-resins.—M. Bonas- 
tre who has made some interesting experiments on thissubject, 
has given the name of sub-resins, to those which are entirey 
deprived of essential oil, which are ‘deprived of acid, and 
which are soluble only in boiling alcohol, ether, or the vola- 
tle oils. ‘The property of phosphorescence, when they were 
pounded ina porcelain mortar with a glass pestle, he found in 
gum Elemi, gum Alonchi, and the gum Arbol-a-brea from 
Manilla. In gum Elemi the light was pale and feeble, and 
less than is shown in pounding sugar. In gum Alonchi well- 
