SPONTANEOXTS GENERATION. 291 



them is slightly warmed with a spirit-lamp, and its open 

 end is then dipped into the turnip infusion. The warmed 

 glass is afterwards chilled, the air within the flasks 

 cools, contracts, and is followed in its contraction by 

 the infusion. Thus we get a small quantity of liquid 

 into the flask. We now heat this liquid carefully. 

 Steam is produced, which issues from the open neck, 

 carrying the air of the flask along with it. After a few 

 seconds' ebullition, the open neck is again plunged 

 into the infusion. The steam within the flask con- 

 denses, the liquid enters to supply its place, and in 

 this way we fill our little flask to about four-fifths of 

 its volume. This description is typical ; we may thus 

 fill a thousand flasks with a thousand different infusions. 

 I now ask my friend to notice a trough made of 

 sheet copper, with two rows of handy little Bunsen 

 burners underneath it. This trough, or bath, is nearly 

 filled with oil ; a piece of thin plank constitutes a kind 

 of lid for the oil-bath. The wood is perforated with 

 circular apertures wide enough to allow our small flask 

 to pass through and plunge itself in the oil, which has 

 been heated, say, to 250° Fahr. Clasped all round by 

 the hot liquid, the infusion in the flask rises to its 

 boiling point, which is not sensibly over 212° Fahr. 

 Steam issues from the open neck of the flask, and the 

 boiling is continued for five minutes. With a pair of 

 small bi-ass tongs, an assistant now seizes the neck near 

 its junction with the flask, and partially lifts the latter 

 out of the oil. The steam does not cease to issue, but 

 its violence is abated. With a second pair of tongs held 

 in one hand, the neck of the flask is seized close to its 

 open end, while with the other hand a Bunsen's flame 

 or an ordinary spirit flame is brought under the middle 

 of the neck. The glass reddens, whitens, softens, and 

 as it is gently drawn out the neck diminishes in dia- 



