3 1837] Instruction in Geological Investigation. $23 
cise, I believe, to the conscience as well as to the observing 
faculty. 
Innumerable problems arise during this work: they are only 
— too plentiful. The quality of the student may be finely gauged 
_ by the kind of questions they excite in him; it is needless to add 
that the quality of the instructor may be gauged by his answers! 
As a general rule, the answers should be like guide-boards point- 
_ ing out the way to the settlement; not like coaches, carrying the 
_ Passive questioner there : the working geologist must learn to go 
afoot, and to find his road rather than be led along it. I may be 
allowed in closing a single illustration from an actual case. 
The problem in hand was concerning the former higher level 
of the sea about Boston. The opinion is commonly entertained 
, that there was a post-glacial depression of the land amounting to 
about ninety feet; this being quoted from an old record of sea- ' 
_ Shells found at that altitude near Winthrop, and confirmed by 
i comparable records to the north and south. If such a depression 
_ Occurred, the shore of the sea must have run around the margin 
of the present Boston basin. With this beginning, the student is 
_ Sent into the field, to search the slopes up to one hundred feet 
, for water-marks, and to search his mind for argument on the 
whole question. He must be on the alert to perceive any faint 
 Mdication of a rock-cliff, sand-bar, or delta; he must keep his 
_ Mind wide open to all available hypotheses for their explanation, 
_ “¥en the most “ cranky” being dismissed only for cause, not be- 
a 
e 
a it is unfashionably dressed; he must be strictly logical and 
“Mpartial in applying tests to verify his hypotheses, and he must 
‘Sive up all that are found wanting. To the first view, the tramp- 
— NY over the country may seem the greater part of the field-work, 
i “Xercise is al 
i Students find 
to one who is able to take the full profit from it, the mental 
ways much greater than the physical. Some 
And the physical work the harder of the two. 
discussion will run about as follows: Admitting that the 
: i inthrop shells are a true sea-deposit, there ought to be signs 
the Shor 
ore somewhere above the present level, unless 
€ did not stand at any level long enough to make a 
: pied b table mark, or unless the Boston basin was mostly occu- 
Y glacial ice during the depression. Supposing that a 
mark was made, what would be its appearance? The 
_“Pegraphy of the present shore-line has to be consulted, and 
XXL—no, 9. : 
56 
