1 92 On the Porosity of Glass, ire. 



3 parts paper pulp, 4 glue, 4 white bole earth, and 4 

 chalk, oil f produce an unifornn sheet, as hard as iron. 



1 paper pulp, 1 glue, 3 white bole earth, 1 linseed oil ; a 

 beautiful elastic sheet. 



When 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, they 

 were hardly altered in form, and were converted into black 

 and very hard plates. — Tech. Rep. 11. 421. 



1 7. On the porosity of glass and siliceous bodies.— Mr. 

 Deuchar, in a paper on the occasional appearance of wa- 

 ter in the cavities of crystals, and on the porous nature of 

 quartz and other crystalline substances, read before the 

 Werrierian Natural History Society, suggests that the crys- 

 tals which are found to contain these portions of water, 

 were probably once hydrated, or rather contained through- 

 out their mass an excess of water, and that this fluid having 

 afterwards separated from the crystals, passed by cap- 

 illary attraction, either to the surface, or to any accidental 

 void space within them, 



Mr. Deuchar, thinks it obvious that the water might 

 pass through the crystals, not only from the porous nature 

 of their particles, but also from their temporary display of 

 rents, during the applicatiou of a high temperature. It is 

 supposed that all siliceous bodies, even glass &:c. are po- 

 rous, and the author thinks that the filling of well stopped 

 bottles when sunk to great depths in the ocean, depends 

 on the water passing through the glass, and not through the 

 materials used to stop the bottles, though 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, 1 15, 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 

 cavities of the slags from iron furnaces, are pure titanium. 



19. Congelation of Mercury. — M. Gay Lussac states in 

 a memoir on the cold produced by the evaporation of 



