238 Transactions of the Royal Microscopical Society. 
in the form of mattresses 2} inches thick, made up ready for use. 
Those who must handle it ought certainly to be provided with 
thick gloves, and great care should be taken not to inhale its fine 
dust. 
The rapid cooling of this silicate cotton in its process of forma- 
tion might be expected to give it polarizing properties, but it only 
possesses them in a feeble degree. 
