808 Royal Soctety of Edinburgh. 
2dly, That nature produces, by a direct process, all simple and 
compound crystals, without first forming a nucleus in the latter. 
3dly, That the matter, serving to form the crystals, is in the 
state of a solid mass before, and continues in that same state 
during the whole process of crystallization. It may be called 
crystallizalle matter. 4thly, That crystallizalle matter is that 
which has filled, by infiltration, the chasms and clefts of moun- 
tains, and the cavities of rocks; which composes the veins, the 
stalactites, and the stalagmites; and, in general, all that which 
constitutes accidental formations found in blocks, nodules, &c. 
within large masses.” 
He recommends for his crystallogenous process, ‘‘ a bed one 
inch thick, composed of loose earth, obtained from the decom- 
position of the stone in which the erystallizable matter is found, 
having an elevated brim of the same material round it, one-third 
of an inch in height. Some balls made of the same earth are 
disposed here and there on this bed, on which are placed various 
pieces of solid crystallizable matter, formerly known under the 
name of crystalline matrix. On these pieces other balls are 
properly disposed, serving to support some more speeimens of 
crystallizable matter, so arranged as not to touch each other. 
The whole of it is then made as solid as possible, by the addition 
of other large and small balls, introduced wherever any space 
exists ; and lastly, the apparatus is surrounded by a wall of bricks 
laid singly on each other, without any mortar, and in a way to 
admit a free circulation of air. 
«¢ Every two or three days the whole apparatus is watered, 40 
as to keep it in a state of constant humidity, and no more. A 
degree of temperature is maintained equal to the internal tem- 
perature of the earth ; and the apparatus is examined every fort~ 
night or three weeks; when, if necessary, the pieces may be care- 
fully washed and replaced, taking care to arrange them so, that 
the balls which before were under, may now be placed above, | 
After a certain lapse of time, the crystallizable matter is found 
to present distinct and beautiful crystal of the substances ém- 
ployed.” 
ROYAL SOCIETY OF EDINBURGH. 
Papers on the following subjects have been read at this S0- 
eiety since the commencement of the present session : 
On the Optical Properties of Fluate of Lime and Muriate of 
Soda; by Dr. Brewster. The author has ascertained that this 
elass of crystals possesses the property of double refraction. 
Large masses of muriate of soda, fluate of lime, alum, and dia- 
mond not only possess this property, but doso in a manner dif- 
ferent 
