The J]Jicroscopc. 357 



to salurate it, and being perfectly dissolved, let it rest foi- a few 

 liOLirs; the solution being thus prepared, take up a single drop 

 and place it on a slip of glass; spread it gently over the glass, as 

 level as possible; hold it near a fire or candle, to give it a gentle 

 heat. When the edges begin to look white having your microscope 

 ready, place the glass, and you will see the formation of the crys- 

 tals; when the action once begins, the eye should not be taken 

 off, for the figures, in forming, alter every instant till perfect. If 

 you provide yourself with several small bottles, a collection of 

 the solution of the different salts may always be in readiness for the 

 microscope, and by a variety of combinations, you may produce 

 several thousand subjects for examination — a sight no one can 

 behold without delight. As soon as they become formed, they 

 are either cubes, rhomboids, pyramids, or certain regular fig- 

 ures, showing always the same sides or angles, in different sub- 

 stances. The following are the best for this ])urpose. Nitre, 

 rock salt, Glauber's salt, sal ammoniac, hartshorn, green vitriol, 

 white vitriol, and salt of amber. 



The following description of the formation of the crystals of al- 

 um is taken from Mr. Baker's work on the microscope. ' The 

 configurations of this salt abound with beauty and variety; place 

 a drop of this solution on the glass, and, gently heated, it exhibits 

 at the beginning, a dark cloud, which appears in motion near the 

 edge, and runs swiftly through to the right and left, till they join; 

 these, when examined, appear to be salts shot into slender lines^ 

 which cross one another at right angles. 



' Crystals of Silver. These form a beautiful opaque object. 

 In a drop of nitrate of silver, put a fine piece of copper wire, or 

 the point of a pin; place it directly under the microscope, and the 

 crystals will extend till the fluid is evaporated; this object may be 

 permanently preserved: take a piece of Bristol card paper of the 

 required thickness and of the same size as the glass to which it is to 

 be fixed; punch an aperture in the centre of the card, then, with gum 

 or paint, fix it upon the glass, place a drop of the solution of ni- 

 trate of silver within the aperture into which drop a small particle 

 of copper; when the crystals have formed and the evaporation 

 subsided, cover the aperture with glass or talc. 



'By dissolving any mineral in muriatic or nitric acid, and plac- 

 ing it under the microscope, you will perceive beautiful crystals 

 formed. 



'Common Salt. Place a single drop of water in a glass, 

 and put a few panicles of common salt in it; give it a gentle heat 

 till the water is evaporated, and you will have beautiful crystals 

 in tlie form of cubes. Epsom salt will' be formed into six-sided 



