- duced by cultivation. 
APRIL 4, 1884.] 
volume has been prepared in obedience to this 
requirement : itis, in part, based on work under- 
taken by Dr. Smith in 1880, in the prepara- 
tion of reports on cotton-culture in Alabama 
and Florida for the tenth census of the United 
States. The maps and woodcuts engraved 
for the census-office, and the statistics collect- 
ed by the enumerators, were placed at his 
disposal for this report; while the geological 
material collected by the state survey during 
previous years was freely contributed to the 
census.report on Alabama. Subsequently ad- 
ditional work has been done by the state sur- 
- yey for this report; and the resulting volume 
is most creditable, both to the ability of Dr. 
Smith, and the wisdom of the state in institut- 
ing such a survey. 
Part i. of the report is introductory in its 
character, and consists of a general discussion 
of the composition, mode of formation, and 
properties of soils, and of the changes pro- 
This discussion, extend- 
ing over one hundred and fifty-three pages, is 
admirable of its kind. It does not attempt to 
present any original observations ; but it is a 
very full and judicious résumé of the present 
state of knowledge on these topics, and shows 
a much greater familiarity with them than is 
usually expected from the geologist. 
Part ii., which constitutes the report proper, 
is an account of the main agricultural features 
of the state of Alabama. Following the tab- 
ulated results of the census enumeration, — 
viz., table i., area, population, tilled lands, and 
cotton-production ; and table il., acreage and 
production of leading crops, —we find section i. 
devoted to an outline of the physical geography 
and geology of the state, and an enumeration 
of its agricultural subdivisions; section il. 
giving a detailed description of these agricul- 
tural subdivisions ; section ili., agricultural de- 
scriptions of the counties of Alabama; and 
section iv., cultural and economic details of 
cotton-production. 
For the purposes of agricultural description, 
Dr. Smith divides the state into three divisions, 
—a middle, a northern, and a southern. Of 
these, the middle division is the oldest geologi- 
cally, and consists of the south-western ter- 
mination of the Appalachian chain; and the 
northern is the next in order, consisting of the 
southern termination of the great Cumberland 
tableland and of the highlands of Tennessee, 
together with the Warrior coal-basin. With 
the exception of bottom and alluvial lands, 
the soils of this division are sedentary soils, 
resting upon the rocks from which they were 
formed; and both the agricultural and topo- 
SCIENCE. 
419 
graphical features of the country are largely 
determined by its geological structure. 
In the southern division, on the contrary, 
these features are largely independent of geo- 
logical structure, and ‘‘ almost exclusively the 
result of erosion as determined by differences 
in the material of a single formation, — the 
stratified drift or Orange sand, which, except 
in parts of the prairie belt, covers the under- 
lying beds over this whole division.’’ 
The soils of each of these regions are very 
fully described, the description being in many 
cases accompanied by chemical analyses and 
determinations of the more important physi- 
cal properties. In the middle and northern 
divisions the classification is chiefly geological, 
while in the southern it is based mainly on the 
character of the prevailing forest-growth. A 
valuable addition to this portion of the report 
is a list of trees and lesser plants characteristic 
of the several regions of the state, prepared by 
Dr. Charles Mohr of Mobile. 
The report is illustrated by three geological 
sections, an agricultural map of the state, and 
maps showing the distribution of temperature 
and rainfall for the year, and also for the winter 
and summer seasons. 
LATE ELECTRICAL BOOKS. 
Absolute measurements in electricity and magnetism. 
By ANDREW Gray. London, Macmillan, 1884. 
16+207 p., illustr. 24°. 
Notes on electricity and magnetism. By J. B. Mur- 
pock. New York, Macmillan, 1884. 8+189p., 
illustr. 16°. 
Mr. Gray’s book on absolute measurements 
is the outcome of a series of articles from his 
pen, upon the measurement of currents and 
potentials, published in Nature in 1882 and 
1883: it is, in fact, a reprint of these articles, 
with some alterations and considerable and 
important additions ; and it must be regarded 
as a most useful contribution to what may be 
called the available literature upon this subject. 
The presentation of the systems of compu- 
tation, based on the so-called absolute units, 
is clear and accurate, and will enable the stu- 
dent to obtain a firmer grasp upon the methods 
now all but universally used than can easily be 
secured from other sources. 
The work opens with a description and dis- 
cussion of methods of determining the hori- 
zontal component of the earth’s magnetism, 
upon which so many electrical measurements 
are made to depend. Mr Gray is a warm 
advocate of the use of small masses in this 
operation, suggesting the use of magnets of 
