42 REPORT—1849. 
found that a larger relative amount of the carbonate of magnesia had been taken up 
by the solvent than of carbonate of lime. 
From these experiments the Professors Rogers infer that the infiltering rain-water, 
with its slight charge of carbonic acid, in passing through or between strata of mag- 
nesian limestone, will remove the carbonate of magnesia more rapidlv than the car- 
bonate of lime, and that thus the rock will gradually become relatively less magnesian, 
instead of being made to approach the condition of a dolomite, as is commonly main- 
tained. 
Professors Rogers called attention to the fact, that the stalactites in caverns of mag- 
nesian limestone contain only minute quantities of carbonate of magnesia. An exa-~ 
mination of those in Weyer’s cave in Virginia had proved that while the milky white 
opake stalactites contain a small but measurable amount, the sparry and more trans- 
parent kinds are almost destitute of a trace of this ingredient. It is evident that in 
such cases the carbonate of magnesia is carried off by the liquid below, and that such 
is the case seems to be confirmed by the fact of the large amount of carbonate of 
magnesia found in the springs in the immediate neighbourhood of the cave just 
named. 
5. A fact of much interest noticed in these experiments is the comparative readi- 
ness with which the magnesian and calcareo-magnesian silicates yield to the decom- 
posing and dissolving action of carbonated water and even simple-water. This ex- 
plains the rapid decomposition of most rocks composed of hornblende, epidote, &c., 
without calling in the agency of an alkali, and it enables us to trace the simple pro- 
cess by which plants are furnished with the lime and magnesia they require from soils 
containing these silicates, without our having recourse to any mysterious decom- 
posing power of the roots of the growing vegetable. 
6. In their tache experiments, the Professors Rogers ascertained that the powder of 
anthracite, bituminous coal and lignite all yielded a discernible amount of alkali to 
the carbonated water, while the ashes of these materials, similarly treated, gave no 
alkaline trace on the test-paper. This they think is at once explained by the high 
temperature at which the ash is formed, which by experiments already noticed is 
quite sufficient to dissipate any portion of alkali or carbonate originally present in 
the material. 
On the Allotropic Condition of Phosphorus. By Prof. Scnrorttrer of Vienna. 
This communication being already before the world in the ‘Annuaire de Chimie’ of 
Millon and Reiset, it is unnecessary to do more than briefly state the facts, which Prof. 
Schroetter illustrated by experiment. When phosphorus is exposed to light or heat, 
it is found that a peculiar change of colour takes place, and that although it under- 
goes no chemical change, a very remarkable physical difference is found to have 
ensued, The ordinary yellow phosphorus is highly inflammable. The allotropic red 
phosphorus was not ignited by friction, nor by those agents which acted energetically 
upon the common variety. 
On the combined Use of the Basic Acetates of Lead and Sulphurous Acid in the 
Colonial Manufacture and the Refining of Sugar. By Dr. Scorrern. 
Dr. Scoffern, after a few preliminary remarks on the anomalies which beset the 
colonial manufacture of sugar, stated the actual amount of pure white and crystalliz- 
able sugar existing in the sugar-cane juice to be from 17 to 23 per cent., and the 
amount of juice contained in the cane to be about 90 per cent. Of this amount 
only 60 per cent. on an average is extracted, and of this quantity only one-third 
part of its sugar is obtained, in a dark impure condition, instead of white and pure, 
as it might be extracted. ‘The operation at present generally followed in the 
colonial production of sugar involved the use of lime, an agent which, although 
beneficial in separating certain impurities and decomposing others, effects both these 
agencies at the expense of two-thirds of the original sugar. 
Various plans had been followed to avoid the use of lime; alumina in its hydrated 
condition had been employed, but with inconsiderable success. As a purifying agent 
the basic acetate of lead was known to be most potent, but could not be generally 
employed, owing to the existence of no efficient means of separating any excess of 


