IN CHEMISTRY. 1 03 



13. What test should be employed before going down in an 

 old well or cellar ? 



A lighted candle should be lowered. If that is dimmed 

 or extinguished it is not safe for one to descend. 



14. What causes the sparkle of wine and the foam of 

 beer ? 



The CO 2 formed in the process of fermentation. 



15. What causes the cork to fly out of a catsup bottle? 

 The CO 2 which is produced when the catsup ferments. 



they soon exhausted the oxygen, and impregnated the water with carbonic 

 acid, it was necessary to change it daily. In this operation they suffered the 

 most intense fear. For a few weeks they would drag out a dubious exist- 

 ence, seemingly anxious only to find out before they died where they were and 

 how they got there. Finally, but a few years since, it was discovered that 

 plants evolve oxygen and consume carbonic acid in the water as well as in 

 the air. Starting out with this idea, about the year 1850, a Mr. Warrington, 

 an Englishman, set about breeding fish and mollusks in tanks by the aid of 

 marine plants. He succeeded admirably for a few days, but after a time, a 

 change came over his little world. Without apparent reason, the water 

 became suddenly impure and the fish died. Here was a new agency at work. 

 With the aid of a microscope, Mr. Warrington explored his tank for the 

 poison that was evidently latent there. He soon discovered that some of his 

 plants had reached maturity and, in obedience to the law of nature, had died. 

 The decaying matter was the poison of which he was in search. How was 

 this to be counteracted ? In nature's tanks seas, rivers, and ponds reflected 

 Mr. Warrington, plants must die and decay, yet this does not destroy animal 

 life. We must see how nature remedies the evil. He hastened to a pond in 

 the vicinity and examined its bottom with care. He found, as he had antici- 

 pated, an abundance of vegetable matter decayed. He likewise found 

 swarms of water-snails doing duty as scavengers, and devouring the putre- 

 fying substances before they had time to taint the water. Here was the 

 secret ; so beautiful a contrivance that it is said Mr. Warrington, with the 

 emotion of a true man of science, burst into tears when it flashed upon him 

 like a revelation. 



" He, however, quickly dried his eyes, gathered a quantity of snails, and 

 threw a handful into his little tank at home. In a single day the water was 

 clear and pure again. The fish throve and gamboled, grew and multiplied ; 

 the plants resumed their bright colors, and the snails not only rollicked in an 

 abundance of decaying branches, but laid a profusion of eggs, on which the 

 fish dined sumptuously every day." 



