378 Scientific Intelligence—Miscellaneous. 
blishment of the fact, that it was not manna, but potato sugar. Its 
aspect, taste, fermentability (mannite not being fermentable), and 
the presence of the sulphate of lime, proved this. Biot submitted 
it to a very careful optical examination, and found its characters to 
be those of a starch sugar. Manna contains two kinds of saccharine 
matter, one called mannite, and the other a fermentable sugar. 
Now, mannite, when pure, has no rotative power on polarized light, 
but commercial manna has a slight effect, owing to the presence of 
a small quantity of fermentable sugar. This fictitious substance, 
however, had the same effect on plane polarized light, as sugar pre- 
pared by the action of acids on starch, when the action is arrested 
at the first phase of its transformation.—(Pereira’s Lectures on 
Polarized Light.) 
23. Polarized Light used in detecting Vinous Fermentation.— 
Take a solution of cane sugar, which has right-handed circular po- 
larization. As soon as it begins to ferment, it loses this property, 
but acquires left-handed polarization. sre iis s Lectures on Po- 
larized Light.) 
24. The use of Polarized Light as a Test for Sugar.—Some, 
kinds of sugar, when dissolved in water, yield solutions, which have, 
in a greater or less degree, the property of rotating the planes of 
polarization, some to the right, others to the left. Hence, polarized 
light may be sometimes used as a test of the presence of sugar, and 
the degree of rotation becomes an indication of the quantity and even 
quality of the sugar present. Biot examined by this test a specimen 
of sugar-cane juice, and found that it indicated the presence of 20 
or 21 per cent. of sugar. Peligot subsequently analyzed it, and 
found 20:9 per cent. of sugar. Biot, therefore, suggests that those 
who make, as well as those who refine sugar, might resort to this 
test as a means of determining the amount of sugar in different 
juices or solutions. To the colonist, it would prove useful, by 
pointing out the saccharine strength of the juice at the mill, and to 
the sugar refiner it would be valuable, by enabling him to deter- 
mine the absolute strength of raw sugar.—(Pereira’s Lectures on 
Polarized Light.) 
25. The Value of the Microscope for detecting the best kinds of 
Wool for Felting.—Microscopic discoveries have been made within the 
last few years, which have led to a revelation of much of the mystery 
of felting. Examined through a powerful microscope, the short 
fibres exhibit the appearance of a continuous vegetable growth, 
from which there are sprouting and all tending in one direction from 
the root to the other extremities, numerous leaves like calices or cups, 
each terminating in a short point, It is easy to perceive how easily 
one of these fibres will move in the direction from root to point, 
el Ot eh 
