730 



THE MICROSCOPE. 



Indurated Sandstone, Howth. 



Indurated Sandstone, Bromsgrove. 



Gibraltar rock. 



Granite, various localities. No. 160. 



Hornblend Schist. 



Labrador Spar. 



Norway Rock. 



Quartz Rock, various. No. 159. 



,, in Bog Iron Ore. 



Quartzite, Mont Blanc. 

 Sandstone, Plate VIII. No. 158. 

 Satin Spar. 



Selenites, various colours. 

 Tin Ore, with Tourmalin. 



VEGETABLE SUBSTANCES. 



Cuticle of Leaf of Correa Cardinalig. 



,, „ Dentzia scabra, 



PI. VIII. No. 173. 



„ „ Elaeagnus. 



„ „ Onosma taurica. 



Equisetum. No. 174. 

 Fibro cells from orchid. No. 169. 

 ,, Oncidium bicallosum. 



Sealariform vessels from Fern. 

 Scyllium. No. 177. 

 Silicious Cuticles. — Various. 

 Starch. — Various. No. 167. 



Yery interesting results will be obtained by combining 

 two or more chemical salts. Mr. Davies 1 succeeded in 

 forming numerous beautiful double salts in the following 

 manner. To a nearly saturated solution of the sulphate 

 of copper and sulphate of magnesia add a drop, on the 

 glass-slide, and dry quickly. To effect this, heat the 

 slide so as to fuse the salts in its water of crystallisation, 

 and there remains an amorphous film on the hot glass. 

 Put the slide aside and allow it to cool slowly ; it will 

 gradually absorb a certain amount of moisture from the 

 ah, and begin to throw out crystals. If now placed 

 under the microscope, numerous points will be seen to 

 start out here and there. The starting points may be 

 produced at pleasure by touching the film with a fine 

 needle point, so as to admit of a slight amount of moisture 

 being absorbed by the mass of salt. Development is at 

 once suspended by applying gentle heat; cover the 

 specimen with balsam and thin glass. The balsam should 

 completely cover the edges of the thin glass circle, other- 

 wise moisture will probably insinuate itself, and destroy 

 the form of the crystals. 



Mr. Thomas succeeded in crystallising " the salts of 

 the magnetic metals " at very high temperatures, which 

 gave interesting results, and produced curious forms of 

 crystals. Plate VIII. No. 163 are representations of 

 crystals of sulphate of iron and cobalt, No. 165, of nicke] 

 and potash, obtained in the following manner : — To form 

 the sulphate of iron crystal, add to a concentrated solution 

 of iron a small quantity of sugar, to prevent oxidation. 

 Put a drop of the solution on a glass slide, and drive out the 



(1) Quart. J our n. Micros. Scien., vol. ii. p. 128. 1862. 



