Description and Analysis of the Sillimanite. 113 
prepared so as not only to keep for many months, but also 
so as to retain its original color and delicacy. 
hen the Jeaves of the cabbage are digested in warm 
alcohol, the coloring matter is entirely dissolved, and we 
obtain a tincture of a reddish color, but which, on exposure 
to the air, becomes blue. ter having distilled off a 
portion of the alcohol, the remainder should be evaporat- 
ed, at a very gentle heat, until there results a mass of the 
consistence of a thick syrup. The extract obtained in 
this manner, when put up in closely stopped bottles, may 
be preserved for years. In order to use it, it is only ne- 
cessary to add a small portion of it to water, in which it is 
readily soluble, when the addition of an acid or an alkali 
will produce its peculiar effect. When we wish to em- 
ploy this test to discover small quantities of carbonic acid 
it is necessary to render it slightly green by the addition 
of a diluted alkali. The carbonic acid will then restore 
the blue color, by saturating the alkah. Test papers may 
also be prepared by means of the alcoholic tincture of the 
cabbage, which, when rendered green by immersion in a 
diluted alkaline solution, may be used in all those cases 
ich litmus papers are commonly employed. _ 
Arr. VIII. Description and Analysis of the Sillimanite, a 
new mineral, By Grorce T. Bowen, of Providence. 
Read before the Academy of Natural Sciences, of Philadelphia, on the 
6th of April, 1824, 
Introductory Remarks. 
On receiving the following article, I was impres- 
quested me to consent to its republication here. ad the 
name, originally proposed for it, at Vew-Haven, or any 
Vou. VIII. No. 1. 15 
