320 FRAGMENTS OF SCIENCE 



mj proposed co-inquirer my friend. With him at my 

 side, 1 shall endeavor, to the best of my ability, so to 

 conduct this discussion that he who runs may read and 

 that he who reads may understand. 



Let us begin at the beginning. I ask my friend to 

 step into the laboratory of the Royal Institution, where 

 I place before him a basin of thin turnip slices barely cov- 

 ered with distilled water kept at a tem- 

 perature of 120° Fahr. After digesting 

 the turnip for four or five hours we 

 pour off the liquid, boil it, filter it, and 

 obtain an infusion as clear as filtered 

 drinking water. We cool the infusion, 

 test its specific gravity, and find it to 

 be 1006 or higher — water being 1000. 

 A number of small clean empty flasks, 

 of the shape shown on the margin, are before us. One of 

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

 end is then dipped into the turnip infusion. The warmed 

 glass is afterward chilled, the air within the flask cools, 

 contracts, and is followed in its contraction by the infu- 

 sion. Thus we get a small quantity of liquid into the 

 flask. We now heat this liquid carefully. Steam is pro- 

 duced, which issues from the open neck, carrying the air 

 of the flask along with it. After a few seconds' ebulli- 

 tion, the open neck is again plunged into the infusion. 

 The steam within the flask condenses, 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 thou- 

 sand different infusions. 



I now ask my friend to notice a trough made of sheet 



