JAMES DWIGHT DANA. 605 
papers are strictly mineralogical, and but five were devoted to 
zoology, while of geological papers and books, there are nineteen 
between 65 and ’75, thirty-three between ’75—’85, and in the last 
decade of his life thirty-one, making a total of 120 titles in the 
geological list, an average of two per year for the whole period 
of sixty years of his literary activity. 
Mineralogy, which first attracted his interest, was early per- 
fected into a system, and after the time of his taking the professor- 
ship in Yale college he wrote few special papers on mineralogy, 
and thereafter turned his attention more and more to geological 
studies. The 4th edition of the System of Mineralogy appeared 
in 1854 with the fully perfected chemical classification. The 5th 
edition, which included the complete systematic description of 
known mineral species, was prepared with the assistance of Pro- 
fessor G. J. Brush, and in the preparation of the 6th edition by 
his son Edward S. Dana, he was unable to take an active part. 
His chief zodlogical works were the reports ‘““On Zoéphytes”’ 
and “On Crustacea” of the Wilke’s exploring expedition; the 
former was published in 1846, the latter in 1854. A considerable 
number of papers were written ‘“On Cephalization,” in which he 
was deeply interested up to about 1866, after that date he pro- 
duced scarcely anything of purely zodlogical nature. 
Geology is a much more complex and miscellaneous science 
than either mineralogy or zodlogy, and therefore it is difficult 
to so arrange the facts as to exhibit their relation to any single 
common principle. But we believe Dana’s Manual has come 
nearer to the setting forth of such an ideal system of geology 
than has been elsewhere attained. The central ideas in this 
system are: (a) the earth a cooling globe,— (0) contracting as 
ie COONS, = (c) differences of depression and elevation of the 
surface the direct result of the unequal contracting, — (@) oceans 
and continents permanent,— (e¢) trends of shores, of islands and 
mountains, according to system, and expressive of lines of weak- 
ness, and of chief foldings and fractures, (f) epeirogenic and 
orogenic phenomena the direct results of the contracting, — 
(g) climates and currents of the ocean also the effects of changes 
