13 



CHICAGO HYDRANT WATER. 



From a communication on this subject, by H. H. Babcock, in the 

 second number of " The Lens " (Chicago, U. S.), we extract the 

 following observations : — 



" Some species of diatoms, as Tabellaria fenestrate and Fragil- 

 aria Crotonensis, produced in abundance all along the shore of the 

 Lake, are always to be found in the hydrant water. Surirella 

 splendida, Cymatopleura solea, Stephanodiscus Niagara, Asterionella 

 formosa, and a Cymbella, which one may sometimes observe in a 

 shore gathering, are occasionally present. A Melosira, identical 

 with that found in small streams flowing into the lake at Glencoc, 

 is often seen ; Pleurosigma attenuatum more rarely ; while Pleuro- 

 sigma Spencerii, Amphiprora ornata, and a Rhizosolenia are the rarest 

 species. 



" In a word, we receive through the hydrants many of the free, 

 unattached forms, known to be produced along the lake shore, and 

 on streams entering the lake to the north of the city, as well as a 

 few species whose origin has not been determined ; while the 

 stipitate or otherwise attached forms, as Gomphonema and Synedra, 

 though growing in abundance in the vicinity, are seldom repre- 

 sented. 



"I am led to believe that the streams of Northern Illinois, Wis- 

 consin, and even Northern Michigan, are the source whence we 

 obtain some of the diatoms most rarely observed in the hydrant 

 water, and that these forms, coming within the influence of the 

 southerly current of the lake, are brought as far as the crib which 

 stands within the current, but near its easterly edge. In a gather- 

 ing made at the mouth of the Carp river, a stream of Northern 

 Michigan, nearly opposite the island of Mackinac, I have found an 

 abundance of Pleurosigma attenuatum and Spencerii, Surirella splen- 

 dida, and Amphiprora ornata. It is probable that other streams in 

 the vicinity, and to the southward of that named, produce the same 

 species, which, specifically light, are borne by the current as far as 

 Chicago, and that the reversal of the course of Chicago river has 

 caused the lake current opj^osite the city to swerve slightly towards 

 the west, and admitted to the crib the pure water from the deeper, 

 undisturbed part of the lake. 



" Whether the river or lake current, or, as I am inclined to believe. 

 both combined, are the source of these organisms, there seems to 

 be no doubt that so long as there is kept up in the river a mode- 

 rately rapid current from the lake, the city will be provided with 

 water more nearly approaching in purity that at Mackinac and Lake 

 Superior, which is remarkable for its transparency." 



