812 Instruction tn Geological Investigation. 
few who may intend to follow the subject professionally in lat 
years. Let us consider an actual case. The first excursion t 
I commonly take with a class leads us to an old quarry in Somer 
ville, near the Agassiz Museum in Cambridge, where a large dikt 
some forty feet wide, cuts across the beds of the Some vi J 
slates, There may be ten or twenty students in the party, atl 
it should be remembered that they have had a preliminary cours 
in elementary geology, in which nearly all the terms that we hat 
occasion to use have been defined: they are also provided wil 
hammers, compasses, clinometers, note-books, and outline may 
of the district. On entering the quarry, I select two fragment 
of rock: one exhibits a fine, granular texture, with bands of i 
ternating color, and is shown as the type of a bedded, st ae 
or aqueous rock; the other is of crystalline texture, witht 
arrangement in layers, and represents the group of massive, cn 
talline, or igneous rocks; and without further explanation pe 
this, the students are asked to search out the area 0 E 
-each rock, the line of contact and the phenomena exhibited 2%) 
it, and to determine the relations of the two and the sequent 
events in their history. Emphasis is given to the important” 
Personal work, and I take pains to say how much more vale” 
is the ability to determine the facts than the facts thems 
ion from 
fore 
to suggest observations and give encouragement Ber: 
questions. The questions are to be answered by little 
Even the best students are almost helpless at first,—S° 7 
their general education taught them of independent, of y 
servation even of a simple kind. One of the com hich 
ments is, “I don’t know how to go to work,” u i oat 
necessary to repeat that the first step is simply tO search of ¢ 
area of the two rocks and the phenomena of their linei 
