Scientific Intelligence— Miscellaneous. — 817 
two planets. Of the comets, one was discovered at Berlin, two at 
Gottingen, and the fourth was seen very generally with the naked 
eye to the end of last March. None of them have been identified 
with preceding comets.—(From the Right Hon. the Earl of Har- 
rowby’s Address to the British Association at Liverpool.) 
MISCELLANEOUS. 
20. New Method of procuring Coloured Silk from the Cocoons. 
—It has long been known to physiologists that certain colouring 
matters, if administered to animals along with their food, possessed 
the property of entering into the system and tinging the bones. In 
this way the bones of swine have been tinged purple by madder, and 
instances are on record of other animals being similarly affected. 
No attempt was made to turn this discovery to account until lately, 
when Mons. Roulin speculated on what might be the consequences of 
administering coloured food to silkworms just before spinning their 
cocoons, His first experiments were conducted with indigo, which 
he mixed in certain proportions with mulberry leaves serving the 
worms for food. The result of this treatment was successful—he 
obtained blue cocoons. Prosecuting still further his experiments, 
he sought a red colouring matter, capable of being eaten by the silk- 
worm without injury. He had some difficulty to find such a colour~ 
ing matter at first, but eventually alighted on the Bignonia Chica. 
Small portions of this plant having been added to the mulberry 
leaves, the silkworms consumed the mixture, and produced red 
coloured silk. In this manner the experimentalist, who is still pro- 
secuting his researches, hopes to obtain silk, secreted by the worm, 
of many other colours. 
21. The value of Polarization to the Optician and Glass Manu- 
_ facturer.—To the optician, it is of the highest.importance that the 
glass of which lenses and prisms are made should possess uniform 
density, and be free from all defects arising from irregularities in 
the annealing process. To detect these, the glass should be care- 
fully examined by polarized light previous to being ground and po- 
lished, and, by this agent, the slightest defects are made appreci- 
able. So also glass vessels, employed for domestic purposes, may 
be advantageously tested by the same agent.—(Pereira’s Lectures 
on Polarized Light.) 
22. Practical value of the Optical characters of Sugar.—The 
optical characters of sugar have been made use of to detect fraud in 
pharmacy. In 1842, more than a ton of a substance, purporting to 
be manna, was offered for sale in Paris at less than 5d. per pound ; 
the excuse given for the unusually low price was, that cash was im- 
mediately required. Suspicion was raised, and the substance was 
submitted to careful examination, the result of which was the esta- 
