124 
FIFTEENTH REPORT. 
Briefly then the investigation shows that during the summer the sur- 
face oxygen content is between G and 7 cc. per liter; that at 5 meters is 
5 to 5 Yz cc. per liter, at 10 meters 3 cc. and at 15 meters the oxygen 
supply which is early in the summer about 3 cc. per liter becomes de- 
pleted so that by the first week in August only traces are found; also 
that the bottom waters which have at the beginning of the summer less 
than a cc. of oxygen, become entirely depleted. 
The data secured regarding the carbon dioxide content are not offered 
for publication at this time as they are incomplete. However, the re- 
sults of the analyses seem to indicate that Lake Douglas is to be classed 
as a hard water lake with a carbon dioxide distribution similar to 
that found by Birge in Lake Mendota. 
