Correspondence. 
5 ? 
A chair of palasobotany has been established in the University of Cam¬ 
bridge, England, and will be shortly filled by the appointment of Mr. 
Albert C. Seward, B. A., F. G. S., of St.Johns’ College, to the professor¬ 
ship. It is a subject for congratulation that this important and in¬ 
teresting, though new science, will now be represented at one of the old' 
universities of England, and with the advantage of the long established 
Woodwardian museum by its side. 
Akron , 0. E. W. Claypole. 
The need of an elementary work on petrography .—The writer after con¬ 
siderable study on the subject, is convinced that a suitable elementary 
work on the difficult science of microscopic petrography remains to b& 
written. The several works available to the student, purporting to be 
elementary and suited to the necessities of the learner, are indeed, exposi¬ 
tions opening the science in logical gradations of thought. They are 
entirely adequate viewed as memoirs addressed by experts to experts. The 
method and style are those of learned discussions in elaborate treatises,, 
and journals of special scope. It does not seem to be appreciated that the 
style and method of learned exposition are not the best style and method 
for elementary instruction. To make an abstruse subject intelligible to a 
beginner requires fundamentally different handling from that employed in 
addressing a learned society or an expert coterie. Too often the treatises 
called elementary are mere compilations from scientific periodicals or 
books, without any apparent consciousness of the fact that what is good for 
the learned may be very unsuitable for the learner. 
The underlying motive in these elementary treatises seems to be the 
belief that every step must be logically taken, and that no foresight of the 
outcome must be permitted. Authors expect the student to labor through 
a body of abstract definitions, statements and doctrines, before affording 
glimpses of the phenomena which they underlie. Such work can be done 1 
by bright students. The work can be accomplished by any good student, 
provided he have a competent instructor to whom he may turn in case of 
insurmountable difficulty. But the writer holds it to be a first principle in 
the preparation of a book for learners, that it should be made a self-suffi¬ 
cient illumination and guide, and that it should render its subject easily 
accessible, stimulating and attractive. In fact, it should be adequate for 
Selbststudirende. 
In the field of petrographic instruction it might be well to devote an 
introductory course to an exemplification of the phenomena, without much 
if any, attempt to impart the science. The first and most natural thing is 
to show the student th e facts the explanations of which he will receive later. 
Let detailed directions be given as to methods of manipulation. Let a 
large range of observations be provided, embracing every class of phe¬ 
nomena applied in the theoretical exposition which is to follow. Let at¬ 
tention be directed to every feature of the phenomena which may possess 
critical significance. Let observations be multiplied. Let the pupil even 
learn the characteristic behavior of the leading minerals before he is pre¬ 
pared to understand why they behave thus and so. The acquisition of 
such a mere empirical acquaintance with optical characteristics would not 
