192 On the Porosity of Glass, &c. 
3 parts paper pulp, 4 glue, 4 white bole earth, and 4 
chalk, oil? produce an uniform sheet, as hard as iron. 
“1 paper pulp, 1 glue, 3 white bole earth, | linseed oil; a 
beautiful elastic sheet. 
en these plates or slates were steeped in water for 
four months, they were found not to alter at all in weight, 
and when exposed to a violent heat for five minutes, ne 
were hardly altered in form, and were st into blac 
and vey hard plates. Teh: Rep. 11. 
tals ehich are found to contain these seuss of water, 
were probably once hydrated, or rather contained through- 
out their mass an excess of water, and that this fluid harang 
afterwards separated from the crystals, passed by 
illary attraction, either to the surface, or to any aceidebtal 
void space within them. 
ge Lcpahaerh thinks it obvious that the water wate = 
eee | that all siliceou si bettiesy on en glass &c. are ~ 
bottles when sunk to 0. preat depths in the ocean, depends 
on the water passing through the glass, and not through the 
materials used to stop the bottles, thongh these were only 
cork, sealing-wax, and oil-cloth. We would, however, re- 
fer our readers to the paper itself in the Phil. Mag. Vol. 
60, p. 310, but wish them at the same time to read one by 
Mr. Scoresby, in the Edin. Journal, VI, 115, also’ relating 
to sunken bottles. 
18. Metallic Titanium.—Dr. Wollaston has lately dis- 
covered that the small cubic crystals of a metallic lustre 
and reddish colour, which are occasionally found in the 
eavities of the slags from iron furnaces, are pure titanium. 
19. Congelation of Mercury.—M. Gay Lussac states in 
amemoir on the cold produced by the evaporation © 
