1882 .] 
317 
Davis. 
lakes and drift basins : here, as suggested above, a short exposi- 
tion of the generally accepted theory of what drift is and how it 
was deposited is properly introduced ; while its fuller study and 
an examination of the possible causes of the accumulation and 
motion of the great ice sheets of glacial times, are postponed to 
their difficult chapter in Geology. The repetition involved in 
this method of study is a great advantage to the student. 
Elementary Geography has already taught something of the 
distribution of lakes, as for example their prevalence in Minne- 
sota and their absence in Tennessee; then we may ask why are 
they so unevenly placed — why are there any lakes at all — what 
is the cause of their basins ? With the long answer to this w T ill 
come a recognition of the distinct forms and surroundings of the 
different classes of lake basins ; then a key to the irregularity of 
their occurrence ; something of their ancestry and their changes 
with time. The conditions that govern the volume and composi- 
tion of their water are also of interest, and lacustrine faunae are 
worthy of special study as showing the persistence of species char- 
acteristic of marine basins and the effect of isolation upon aquatic 
animals that formerly had a wider range. In this they are com- 
parable to the forms of life on islands : indeed the similarity of 
these problems is noteworthy ; it depends upon a relation that 
may be condensed into the form of a proportion — lakes are to 
oceans as islands are to continents. In the present paper, the 
latter topics will be omitted ; the former suggest ample material 
for a long chapter. 
Review of previous treatment of the subject. To show 
wdiat has been done, as well as to point the necessity of doing more, 
the following abstracts are given from various works on physical 
geography and geology and from special papers. 
It must be borne in mind that these notes refer chiefly to classi- 
fication of basins, and give imperfect indication of how far geo- 
graphic or statistic descriptions are carried ; from the casual 
mention of the subject given in authoritative geological text 
books, it is evident that it cannot be considered geological. In 
addition to the general references given here, others of a more 
special kind will be found farther on : for access to many of the 
latter I am indebted to Professor J. D. Whitney’s kindness in 
