edge of the needle is read off by an eye-glass to a minute of 
arc. There is no difficulty in adapting the reflecting system 
for the purpose of registering minute magnetic disturbances. 
A sketch of the instrument is appended. 
“On the Chemical Formula of Alizarine/’ by Edward 
Schunck, Ph.D., F.R.S., &c. 
The discovery of a mode of preparing alizarine arti- 
ficially, lately made by MM. Graebe and Liebermann, and 
brought before the notice of the Society at its last meeting 
by Professor Roscoe, is not only of the highest importance 
