286 Geology in the High School. — Alde7'son. 
discharge of its waters through the Desplaines and Illinois 
rivers, the lowering of the lake level and the present topogra- 
phy of Cook county. The principle underlying the Chicago 
drainage problem is then clearly understood and an eminently 
practical value is given to the study. The missionary 
work done by this one subject is very great, for the pupils 
invariably instruct their parents who are generally as ill- 
informed as the pupils themselves. 
While the field work is going on, two days of the week are 
devoted to that phase of the work, observation and discussion 
thereon — the remaining three are devoted to a study of min- 
eralogy and lithology. The work is purely experimental, the 
general line ofWinchell's Excursions and Crosby's Common 
Rocks and Minerals being followed. The properties of the 
minerals and the characteristics of the rocks are not learned 
from the book, but from actual tests, and are tabulated for use 
in future investigation. Only those varieties are studied of 
which there are in the school cabinet enough to supply the 
entire class with one or more. The cabinet is somewhat pecu- 
liar in that it has been formed for this particular kind of work. 
It contains few really beautiful specimens and none for show, 
but has fully five hundred specimens of quartz in most of its 
forms, a hundred of the feldspars, an almost equal number of 
the micas, fifty garnets, seventy-five staurotides and others of 
the commoner varieties in almost equal abundance. As soon 
as the pupil acquires a knowledge of a few varieties he is 
required to select these, and give reasons for his selection, from 
a larger number that he has not yet studied. Thus he learns 
to discriminate between what he is sure he knows and what 
he is sure he does not know. Each day he adds to his knowl- 
edge by the study of a new mineral or rock, till finally his 
work consists of identifying a fresh box of assorted specimens 
each day. Soon they become so expert that they can identify 
and describe accurately all the varieties of minerals and rocks 
they will probably ever find and can with some study identify 
new varieties. The limited time — ten months — given to geol- 
ogy demands that the work on minerals and rocks shall stop 
at this point. The sand dunes on the lake shore, the wearing 
away of the crust by the waves, the glaciated surface of the 
bed rock at Stoney island, each starts inquiries upon atmos- 
pheric and aqueous agencies and the Glacial period. These 
