246 Review of Recent Geological Literature. 
showing every possible variation, which will save future confusion. An 
interesting table on page 166 shows the stratigraphic distribution of all 
the Cretaceous Ostreiche of the region, and at a glance, throws entirely 
new light upon these important forms. In chapter XV, two typical 
species, GrypJuva piteheri Morton, of the lower Cretaceous, and Exo- 
gyra costata Say of the upper Cretaceous are discussed, and the re- 
markable controversy concerning the former, which for years has oc- 
cupied American geologic literature is review^ed and the confusion sur- 
rounding this important species, dispersed. 
It is impossible to review at length the data here presented for the 
first time of the detail of the basal Tertiary and the Quaternary forma- 
tions. They describe these features as they are, and throw new light 
upon them. They are as valuable as the Cretaceous discussion, 
and give the first local description and section ever published from 
that region. 
Part II of the report, in the writer's opinion is as important as the 
first, and consists in a discussion of the economic features. It contains 
a scientific treatise upon the origin and classification of soils and describes 
in the language of the people every geologic soil of the region, trans- 
ported or residual, and points out clearly their defects or excesses, and 
how they can be remedied, by natural means, i. e. the use of the val- 
uable and untouched beds of gypsum, chalk and greensands, in which 
the volume shows that the region abounds. Inasmuch as nine-tenths 
of the soil of Arkansas is deficient in these very elements, these facts 
are of incalculable value to the agricultural interests of the state. An- 
other remarkable economic fact is the perfect analogy of conditions for 
making Portland cement, existing between this region and the original 
seats of that industry in England, which is further brought out in an 
appendix by Dr. Branner. 
The chemical analyses, by Dr R. N. Brackett, are of importance to the 
geologist, for they give both the composition of the original structure 
and the soil derived from it, thereby permitting the general character 
of geologic areas to be determined, and obviating largely the necessity 
of analyzing every individual farmer's field. Besides these analyses 
are arranged in a systematic geologic sequence so that great light is 
thrown upon the geologic origin of the strata. 
The print of the work is excellent considering the conditions under 
which it is done, but the book has many typographic errors, probably 
due to lack of oversight by its author. Altogether the work is a cred- 
itable addition to the geologic literature of the country, and is espec- 
ially valuable as a key to an almost unknown region and to a much dis- 
cussed section of American geology. 
Solar Heat, Gravitation and Sun-spots. J. H. Kedzie.* 
Having stated his conception of the nature and origin of the heat of 
the sun, the author fills the rest of the volume with arguments and 
illustrations to prove its applicability and validity. His first is a 
* See page 181 for tbe commencement of this review. 
