LEVITON, WOGAN, & ALDRICH: SCIENTIFIC BIBLIOGRAPHY OF THE ix 
CALIFORNIA ACADEMY OF SCIENCES, 1854-2010 
MEMOIRS 
California Academy of Sciences 
VOL. I. 
SAN FRANCISCO 
M E M O I R S 
l J REPUTE(.) TO TUB CALIFORNIA ACADEMY OR SCIENCES. 
II. Principles of the Natural System of Volcanic Rocks. 
IIy F. Bahon Richthofen, im. rmr,. 
[Presented. M«y I’.tli, lSf.7,1 
I NTRODUCTORY. Among the features peculiar to modern Geology may be noticed 
a revival of that speculative tendency which prevailed among the cultivators of this 
science at the close of the lasL century. But while in those early times imagination 
exerted a dominant influence in the framing of hypotheses, and discussions between 
the adherents of different doctrines were conducted with all the bitterness peculiar to 
such struggles, when neither party has a firm basis upon which to found its arguments, 
the constant ascendency of the spirit of the inductive method has imparted to those 
theories more recently propounded a more logical and scientific form, while, at the 
same time, the increasing amount of positive knowledge lias given to the different 
doctrines a more varied and more definite character, and enlarged the scope of dis¬ 
senting views. 
This renewed tendency to systematize and theorize, which is especially con¬ 
spicuous in the records of the last twenty years, must be ascribed, partly, .to the vast 
amount of well-established facta gathered during the previous decades, and which 
have since been multiplied and intensified in a constantly increasing ratio, ns regards 
depth and distinctness of observation as well as the geographical area over which they 
extend'; partly, and in no less degree, to the rapid progress made by those sciences on 
which geology has to draw for the general laws which are alone capable of affording a 
philosophical guide to speculation on the basis of facts gained by observing and com¬ 
paring. J'he advance of the chemical and physical sciences, especially, has had a 
B 
Occasional Papers 
CALIFORNIA 
ACADEMY OF SC 
I. 
SAN FRANCISCO, 
1890. 
A REVISION 
South American Nematognathi 
or Cat - Fishes 
CARL H. EIGENMANN, Ph. D. 
ROSA SMITH EIGENMANN, 
(Curator of Fishes California Academy of Sciences.), 
D 
San Francisco: 
California Academy of Sciences, 
July, 1890. 
