Review of Recent GeoUxjical Literature. 321 
tory paper, by the late Prof. Williams, he states his conclusion that the 
eastern part of the United States has no truly plutonic rocks of demon- 
strably younger age than the end of the Paleozoic era, when the Appa- 
lachian mountain belt was uplifted and folded; but they are found in 
abundance of all ages down to that time. From his studies in Maryland, 
as set forth here in detail, Williams was led to believe that pegmatites, 
in some cases produced by aqueous segregation but in other cases by 
igneous intrusion, and quite similar in appearance, occur side by side. 
Summarizing the investigations of the granitic rocks of eastern central 
Maryland, Dr. Keyes finds that some of the granites are eruptive: that 
both epidote and allanite occur in the eruptive granites as original 
constituents: that muscovite is a primary mineral in the very acid 
granites of Guilford, Md.; and that certain gneisses are derived from 
granites, their schistosity being a result of orogenic movements with 
shearing and partial recrN'stallization. w. u. 
Reports on Areal Geology, SJteets 1-4. (Missouri Geological Survey, 
vol. IX, 420 pp., 4 maps, 25 plates, 51 figures, 1892-1896.) The general 
I)lan of publication adopted by the state geologist. Dr. C. R. Keyes, is a 
single series of royal octavo volumes. The plan of the work is of a two- 
fold nature, embraced under what is called subject work and areal 
work. Eight volumes, embracing some of the results of the former, 
have already been published; the present volume is the first of the areal 
reports. As stated in the list of the publications of the Survey, the 
areal (or sheet) rejjorts are issued in three different editions to meet the 
demands of different classes of people, in order to supply the necessary 
wants and at the same time not to compel the issuing of an unnecessar- 
ily large number of each. The editions of the areal reports areas fol- 
lows: 
First. Several reports are bound together, in cloth, with folio topo- 
graphic and geologic maps on thin bond paper and folded, the whole 
forming a volume uniform in size and style with the regular series of the 
final large octavo reports of the Missouri Survey. The first group of 
these areal reports form vohime ix of the regular series, and consists of 
four jjarts, or reports on (1) Higgineville sheet, (2) Bevier sheet, (3) Iron 
Mountain sheet, and (4) Mine la Motte sheet. 
Second. Text same as in the first, Vjound in cloth as volume ix of 
the regular series, but the folio maps are unfolded, printed on heavy 
cardboard, and each enclosed in heavy j)aper covers. 
Third. Text of each report is bound as a separate V)rochure, with 
folio majjs on thin paper and folded. 
The first of the sheet reports appeared in pamphlet foiin several years 
ago and two others more recently. The necessity of a dual arrangement 
of work in completing a thorough geological survey is obvious. On ac- 
count of the magnitude of the work the investigations must necessarily 
extend over a period of several years. The means visually provided are 
far too inadeciuate to extend the detailed work over a whole state in a 
single year, and consequently in the beginning of the work some areas 
