60 REPORT—1850. 
atom becomes expended in producing radiant heat and light before the atom can di- 
vide its motion among the adjacent atoms of phosphorus, for they are so connected 
that they do but slowly and imperfectly communicate their vibrations to each other, 
which is the theoretical way of saying that the substance is a bad conductor of heat. 
The amount of iight, therefore, produced by the oxidation of a newly-exposed cold 
surface of any substance having sufficient affinity for the surrounding gas will be less, 
as its conducting power is greater. 
These considerations indicate that potassium (and of course sodium, calcium, &c.) 
must be phosphorescent, though less so than phosphorus itself, and experiment has 
fully confirmed these anticipations. 
On the Condensation of Volume in highly hydrated Minerals. 
* By Lyon Prayrarr, PhD., F.R.S. 
Dr. Lyon Playfair has been for some time engaged in a series of investigations 
having particular reference to the atomic constitution of bodies. This communica- 
tion was in continuation of this subject. It was shown that the water in hydrated 
minerals was, by some peculiar molecular force, subjected to extreme condensation ; 
that it occupied only the space of the solid matter of the mass; and on dissolving 
any salts containing water of crystallization, it was found that they only increased 
the bulk of the water by the quantity of water they contain, the solid matter appearing 
to occupy no space. , 
Observations on Ropy Bread. By Guorce Reap. 
During the summer and autumn of 1846, the bakers of London made many com- 
pleints repecting a disease in their bread termed ropiness. Having, at the request of 
many bakers, investigated the subject, the author offered the various statements which 
he had collected, and some results of personal observation, for the consideration of 
the Section. Among other facts, he mentions, that on examining some specimens of 
diseased bread with a powerful microscope, he found that the whole of the cellular 
portion of it was destroyed, and its appearance was that of a peculiarly white, lumi- 
nous substance, somewhat resembling the granules of starch. One or two of the 
specimens which he examined were found to be congpletely covered with fungi. 
On the Sugar Produce of the South of Spain, chiefly in connexion with the em- 
ployment of Acetate of Lead and Sulphurous Acid as Purifying Agents. 
By Dr. Scorrern. 
On the southern coast of Spain, in a region limited by Almeria on the east and 
Malaga on the west, bounded on the north by mountain ranges and on the south by 
the Mediterranean, is a tract of land which, so far as its climate and productions are 
concerned, may be aptly denominated tropical. In it the date, palm, indigo, cotton, 
and sugar-cane flourish with vigour, yielding products equal both in quantity and 
quality to those of the tropics themselves, 
The sugar-cane, first introduced by the Arab conquerors, is not only consumed in 
large quantities as a dessert, but also gives rise to a considerable manufacture of raw 
and refined sugar, a circumstance which beyond Spain itself seems to be very little 
known. 
There is perhaps no example on record of any operation involving a commercial 
result, attended with such an enormous destruction of material as the operation of 
extracting sugar from thecane. One portion of this loss is due to mechanical, another 
to chemical causes. 
The sugar-cane has been stated by most writers who have found opportunities of 
practically examining the subject, to contain no more than 10 per cent. of solid non- 
saccharine matter, leaving 90 per cent. of juice to be extracted. Of this 90 per cent. 
most writers concur in testifying, that in practice scarcely 50 per cent. are actually 
obtained, at least in the British West India possessions. Cane-juice itself has usually 
been stated to contain from 17 to 23 per cent. of crystalline sugar, of which scarcely 
7 per cent. in practice were actually extracted. 
Considerable doubts having been expressed as to these statements of the amount of 
