Reviczv of Recent Geological Literature. 257 
Part I, by Dr. Williams, deals with the Paleozoic fauna. He de- 
scribes the fossils from various formations, giving good illustrations, 
but reserves more detailed descriptions for future publication. In this 
paper he discusses especially phylogeny and variation. The boundary 
between Silurian and Devonian was first described in the Welsh series 
in which transition was from calcareous sediments with a marine 
fauna to sandstone with brackish fauna. Dr. Williams now deter- 
mines this boundary for America. The Lower Helderberg in the in- 
terior is closely related to the succeeding fauna, because there was no 
radical disturbance in the marine conditions. It is the Oriskany fauna 
that shows evidences of a disturbance which ended in uplifting large 
areas of marine surface ; and this formation is to be correlated with 
the Gedennian of the Rhenish provinces, and with the base of the Old 
Red sandstone of Great Britain. Thus the Lower Heldetberg is to be 
located positively as Silurian, in spite of the Devonian relationships of 
its New York fauna. The Gaspe and Square Lake limestones of 
Maine both contained evidence of New York Lower Helderberg fauna, 
and both occur below the Devonian boundary line. 
It is to be regretted that Dr. Williams does not institute a compari- 
son between the Upper Helderberg fauna and that of the Ludlow beds 
of England, which represent the typical Upper Silurian as defined by 
Murchison and Sedgwick. Since the Siluro-Devonian boundary may 
now be regarded as established for both countries, a comparison be- 
tween the faunas of equivalent beds would be of interest. 
Part II, by Dr. Gregor\% deals with the volcanics and elastics of the 
Aroostook country. Northeastern Maine is essentially a region of 
sedimentary rocks, yet such igneous rocks as there are, present a 
number of well defined types, and considerable variation in character. 
Dr. Gregory discusses fully the general nature, field relations, petro 
graphy, and chemical composition of the volcanics. The elastics are 
classified on a petrographic basis and mapped from this standpoint, 
their stratigraphic relationships being left until further evidence is ob- 
tained. The structure and history of the region as a whole are not 
touched upon. 
Part III consists of a list of localities wliere outcrops were found, 
and is a most useful addition to a work of this sort. i. h. o. 
Geology in its Relations to Topography. By T. C. Br.\nner. With 
Discussion and Correspondence, Trans. A))fcr. Soc. of Civil Engi- 
neers, XXXIX., pp. 54-95. 
Complaints arc often heard from geologists of the inaccuracy of 
maps. Mr. Branner strikes at the root of this matter in showing the 
necessity of geological knowledge for a successful topographer. There 
is at present no physiographical text book adapted to the needs of en- 
gineers and it is to be hoped that some expert in geolog>' or geography 
will soon meet this demand. Mr. Branner's paper contains a short ac- 
count of some of the simplest physiographic features and supplies in 
untechnical language valuable information in regard to a few of the 
problems which confront engineers. I. H. o. 
