590 Wisconsin Academy of Sciences, Arts, and Letters. 
tion of fig. 13 will show. To the same or a similar series be¬ 
long Bass and Minocqua lakes, and lake Superior (fig. 13) whose 
color has not been rated. 
It is not without significance that the lakes named in the two 
tables may be divided into the same two sets by physical con¬ 
ditions as well as by color. The lakes of the first group receive 
a considerable amount of drainage from streams which pass 
through marshes or they have a good deal of marsh drainage 
from their borders. The lakes of the second set except Green 
lake, have no tributaries, and except Green and Marl, have no 
outlet. They are isolated spring-fed lakes and receive little 
or no marsh water. 
The contrast in the curves of Green lake and lake Geneva is 
an interesting one in view of the general similarity of the 
lakes. The latter lake receives at its western end a large 
amount of spring water which filters through great beds of 
cress and through marsh. No such supply from marshes 
reaches Green lake and the notable difference revealed by the 
spectroscope probably depends on this difference in water 
supply. The tributaries of Green lake in general flow through 
a cultivated farming country and not through marsh. 
The lakes included in table 6, therefore, agree in receiving 
water stained by marshes. Their waters may therefore be 
called marsh-stained waters. One would be inclined to make 
the name more specific and call them peat-stained waters, but 
such designation would go beyond our present knowledge. For 
lakes of the second type no name can be found at present. 
The absorption curves for eleven of the lakes belonging to 
the type with marsh-stained waters, have been put together on 
fig. 12, averaging them according to color rating. The curves 
for lakes rated in color as 6, 8, 14 and 35, show the relation 
which might be expected, so far as wave lengths below 5500 a 
are concerned. The curve for color 22, however, shows a de¬ 
cidedly smaller minimum absorption at 5400 a than the lakes 
with lower color. This relatively small minimum absorption 
is common to Okauchee and Oconomowoc lakes and is shared 
by Lac La Belle (fig. 11, color, 18) and also by North lake 
(color, 35). All of these lakes are on the same stream. North 
lake being the highest and Okauchee, Oconomowoc, and La Belle 
following in order. They show colors of similar type and of 
decreasing intensity through the series. They differ in this re- 
