1887] Instruction in Geological Investigation. RGE 
tact. Not knowing how to go to work on such a problem does 
not mean ignorance of geology alone, but inexperience in the 
first requisite of scientific study. But the most characteristic 
feature of the first day’s work is the frequency with which the 
instructor's authority is appealed to in decision of questions that 
lie open before the class. It is as if the weight of previous 
education were thrown on the side of dulling individual obser- 
vation and judgment. It requires much care to avoid answer- 
ing easy questions and thus defeating the objects of the ex- 
cursion; and it requires more care to escape answering the 
questions without either discouraging or exasperating the ques- 
tioners. A preliminary explanation is advisable, so that all may 
“understand that there is nothing like a rebuff intended in the 
_ tather brusque counter-questions that serve best to direct the 
work where it should go. A student will sometimes come up to 
me, after a very insufficient search for facts on the ground, and, 
_ Presenting a piece of the dike, say, with the idea that he is doing 
his full duty, “Isn’t this melaphyr >?’ Now, as a matter of fact, 
_ he is, in this particular case, quite right; at least, so Í am assured 
: by competent lithologists, and later on he should be told so, but 
Rot at first. He has perhaps heard the name, melaphyr, asso- 
; cated with dark-colored, fine-grained rocks, and makes a lucky 
Venture in using it; but as the object of the work is to train his 
ation, not mine, I throw the burden of proof upon him by . 
asking in return, “ Why do you think so?” “It looks like it.” 
“What is melaphyr?” This may sound, as I now read it, very 
x 
Reg isa snubbing a praiseworthy inquiry; but see the result. 
ine times out of ten the student says, “ Oh, melaphyr ? Mel- 
aphyr is—— I don’t remember ;” and this clears away the PHA 
yy Knowledge that places names uppermost, and brings us down to 
_ * solid foundation for good work. No words must be used that 
_ Cannot be de: 
Tea fined : no suggestions must be made that cannot be 
tited by actual observation. The question may now be re- 
» “If you cannot say that this is melaphyr, what can you 
| ae about it?” “ Well, it is a dike.” “Why do you think so?” 
7 t looks like one.” “What isa dike?” “A dike is a mass of 
Igneous rock filling a fracture in the country-rock.” “ Does this 
“ous rock fill such a fracture?” Again it appears how much 
_ “SET it is to make assertions than to defend them; it is very 
that a student will on his first endeavor suggest and ap- 
