488 
Data are not available for a full comparison of the chemic- 
al constituents of all the waters here under consideration. 
No data whatever are available for Dogfish and Phelps lakes, 
and only sanitary analyses for Quiver and Thompson’s lakes. 
These shed no light on the relative amounts of phosphates and 
carbon dioxid in the water, both important elements in the 
growth of plants. On the other hand, data for a comparison 
of the ammonia and the nitrates are found in Tables XII. and 
XIII. and Plates XLVIII. and XLIX. The nitrates, in so far 
as they are concerned,—as shown in the accompanying table, 
CHEMICAL ANALYSES, SEPTEMBER, 1897, TO MARCH, I899. 
AVERAGES OF ALL ANALYSES——PARTS PER MILLION. 
Thompson’s Lake |Quiver Lake 
BATES TANI OWA i.o setae ore steer cycvore eta siaaeh eee eters 422 .199 
Al buminoid amma Onialient\atue/ejlertnyusetae eto eterna: .546 293 
INTEEIEES Teo 3) ave-e ci sess gone pein cieaie kee SEE oe eee .048 .023 
IND ET ALCS ctccre cy ks oeiemdene oieic peltererteerstenemiere aerate .640 -708 
which gives the averages for coincident periods of examination 
in 1897-1899,— offer no solution for the marked contrast in 
plankton production which the waters in question exhibit, for 
the amounts present differ but shghtly in the two lakes. The 
plottings in Plates XLVIIL. and XLIX. show that the nitrates 
run low during the period from June 1 to October 1, which is 
approximately that of the maximum development of vegeta- 
tion. The averages for this period are .244 and .222 respect- 
ively for Thompson’s and Quiver lakes in 1898. This is almost . 
identical in the two lakes, and may represent an unutilized 
minimum of nitrates, the utilized portion supporting predomi- 
nantly the phytoplankton in Thompson’s Lake and the gross 
vegetation in Quiver Lake. During the remainder of the year 
the contrast between the two lakes in the matter of nitrates is 
more marked, the average being .923 and .684 respectively. So 
far as any contrast appears in the matter of nitrates the waters 
of Quiver Lake are, if anything, a trifle richer than those of 
Thompson’s Lake, 
