362 Messrs Purvis and Black, Oxygen content of the river | 
Description of the Flora, etc., in the riwer Cam. 
During the sammer months, an abundance of aquatic vegeta- _ 
tion grows and flourishes in the river Cam. A long ribbon- 
shaped weed, the Sparganium sp., grows most profusely every- 
where across the whole bed of the river for miles above and 
below Cambridge. Where there are deposits of soft mud, 
especially below the sewage effluent outfall, Zannichellia palustris 
erows well, as does an imported weed Elodea canadensis. 
Conferve are also abundant, and grow well on the soft mud 
below the effluent outfall. 
From October to December the vegetation had almost entirely 
disappeared or it had been removed from the river bed. On 
several occasions shoals of live fish were seen both immediately 
above and below the outfall; and at no time from May to 
December were any dead fish seen below the effluent outfall. 
Mud Deposits from the Sewage Effluent in the river Cam. 
Deposits of black mud were found in patches below the 
effluent outfall. On December 8, before collecting the sample 
of river water at + mile below the outfall, two barges passing 
along the river stirred up a quantity of filamentous bacteria and 
sludge from the bottom. It could be traced along the whole 
4 mile below the outfall. The total solids in the sample taken at — 
4 mile below were estimated to be 9°4 grams per 100,000; and at 
4 mile below the cord to which the thermometer was attached in 
midstream became coated with a gelatinous deposit of masses 
of the same bacteria which had apparently been stirred up by 
the passing barges. Similar filamentous bacteria have been 
shortly described above as having been found in the effluent 
itself. 
We are indebted to Mr Lynch, the Curator of the Cambridge 
Botanic Gardens, for identifying the aquatic flora, and for supply- 
ing the meteorological data. 
