General Science. 899 
frozen in a body of ice, near an opening of water ^ where this 
method might have been of great use. 
45. On the Production qf' Potash from Potato Stalks.^lt 
was lately announced in the philosophical Journals, that in 
France potash had been obtained in great quantities from potato 
stalks. In order to put this to the test of experiment. Sir John 
Hay, Bart, and Dr MacCulloch made a trial on a large scale, 
and found that the quantity of potash was so small, that no 
person could be remunerated by it for the trouble of the pro- 
cess. Messrs Taylors of Queensferry, by desire of Sir John 
Hay, made an experiment on the produce of two acres of po- 
tato stalks, which yielded 2 casks of ashes, weighing S cwt. 
^3 lb. which produced of soluble substance only 36 lb. containing 
a great deal of muriate of potash and sulphate of potash. The 
value of this produce was not more than 2d. per lb. or 6s. in 
all ; and on 12 acres of their own they had a similar result. 
46. Spirits in Glass Jars closed with Bladder^ Mode fcf inu 
proving Wines. — Dr Summering, in a curious set of experiments 
detailed in the Memoirs of the Munich Academy of Sciences, 
has proved, that if mixtures of spirit-of-wine and water in glass 
jars, are covered, some with bladder, and others with paper, that 
the aqueous ingredient escapes through the bladder and leaves a 
concentrated spirit ; while, on the contrary, it is the spiritous 
ingredient which passes through the paper, and leaves little else 
than water. It is proposed to fine and improve wines by expo- 
sing them in vessels covered with bladder or some similar sub- 
stance. In some experiments made with Cyprus wine, a sixth 
part escaped, and the wine was very much improved in quality. 
This mode of improving wines is practised in some parts of 
Suabia. 
47. Method of rendering Glass less BritUe. — A method has 
been published in the foreign journals, for rendering glass less 
brittle, by heating it in water up to the boiling point, and then 
allowing it to cool slowly. In order to try tliis method, we took 
plates of unannealed glass, the mechanical condition of which 
was indicated by the tints which they exhibited in polarised 
light, and we found, that the mechanical condition of glass whe- 
ther annealed or unannedled^ was not capable of being altered 
by the heat of boiling water. In choosing articles of glass, the 
