1886.] NEAV YORK ACADEMY OF SCIENCES. 49 



pounded in the reservoir, became covered with a scum several 

 inches in thickness, consisting largely of Oscillarm. These 

 quickly died, and yielded up a dark-blue coloring-matter {the 

 Plwcocyan of Colin). Finally, this great accumnlation of vege- 

 table growth passed into a state of active decomposition, at- 

 tended with the formation of white foam, and the liberation of 

 large volumes of carbonic acid and other gases. Tlie water, for 

 ten days previous, had been too nauseous to drink, but the whole 

 succession of phenomena above described took place within 

 twenty-four hours, the vast development of algte, their breaking- 

 up with evolution of green and blue coloring-matter, and their 

 final decomposition occurring with astonishing rapidity. The 

 entire reservoir had the appearance of an enormous dying vat, 

 covered with dark-green and blue dye-stuffs, 



A repetition of the same disastrous sequence of events was 

 threatened on September 14th, when the percentage of dissolved 

 oxygen fell to 4c.c., and at the same time a growth of algae 

 began in the reservoir. But meanwhile arrangements had been 

 perfected in anticipation of this catastrophe, and by pumping 

 air under pressure into the mains, the percentage of total dis- 

 solved gases was raised from 1.5.9 c.c. to 21.2 c.c. The green 

 scum on the reservoir disappeared, and the taste and smell of the 

 drinking-water became satisfactory. 



In November. 1S84, a preliminary experiment was instituted at 

 the Fairmount Pumping Station of Philadelphia, an air pump be- 

 ing attached to the main at that point. The aerated water was 

 pumped into the Corinthian Basin through the forty-eight-inch 

 main, a distance of three thousand feet. The results of this ex- 

 periment were so encouraging, that the chief engineer. Col. Lud- 

 low, obtained air-compressors for all the pumping-stations. At 

 only one of them, however, has the process been applied, namely, 

 at Belmont, the other mains being too leaky to permit of its being 

 used. 



At this station the water has been charged with twenty per 

 cent of its volume of air, and the change in composition thereby 

 effected is strikingly illustrated in the following results, which 

 give the composition of the water before it enters the pumping- 

 main and as it is discharged therefrom: 



Parts per 100,000. 



