10£ Mr. C. Tomlinson's Experimental Examination 



manner : — pour 3 drachms of distilled water into a small test- 

 tube, and put into this about 40 grains of sal-ammoniac ; suspend 

 the tube by a piece of twine from the ring of a retort-stand or 

 in any other convenient manner, and carefully boil the solution 

 by means of a spirit-lamp. As soon as the lamp is removed, 

 lower the tube into cold water so as to chill the solution to the 

 crystallizing-point, and, the moment crystals appear at the bottom 

 of the tube, remove it from the water and leave it suspended in 

 the air. The minute snow-storm will soon set in, and will con- 

 tinue for nearly an hour. When the action is over, the tube 

 may be corked and set aside for repetition at some future time. 



These experiments show how important a part sal-ammoniac 

 plays in the storm-glass. The fern-leaf figures and the stars, 

 which are usually referred to the camphor, are produced chiefly 

 by the sal-ammoniac. The stars, moreover, show very decidedly 

 the action of cooling, not of windy weather, as it is said; or if 

 wind has any effect, it is in cooling the storm-glass mixture ; and 

 the appearance of these stars in greater or less galaxies is but a 

 sign of the greater or less, or more slow or more rapid rate of 

 cooling. 



A solution of camphor in cooling gives no definite figures, but 

 flakes very much like snow-flakes, which descend from the surface, 

 and minute particles of camphor, which ascend in such quantities 

 as to make the solution nearly opake. The solution was in the 

 first instance made with 4 ozs. of distilled water, 1 oz. of spirits 

 of wine, and | a drachm of camphor. The solution boiled at 194° 

 for the lower, and 192° for the upper thermometer. When the 

 readings were 136° and 140°, a cloudy appearance set in at the 

 bottom, and multitudes of what looked like air-bubbles ascended, 

 and soon formed ascending and descending currents. When the 

 readings were 127° and 137°, the flakes descended as before 

 described. Next morning the flakes were collected at the bottom 

 as in the storm-glass, and particles were sailing up and down 

 in the clear liquid. The tube was placed in hot water, and 

 the solution was filtered ; it now contained much less camphor, 

 and at 116° and 118° the minute particles appeared, which 

 increased with the cooling, and flakes smaller than those before 

 obtained also ascended and descended in the bright liquid. On 

 the former occasion it was turbid from the multitude of particles. 



Several experiments were made with distilled water, one of 

 which was in a tube 9 inches long, lj inch in diameter; the 

 length of the liquid column was about 1\ inches, 5 fluid-ounces 

 of water being employed, and the temperature of the room was 

 63°. 



