May 17, 1901.] 
magn.; on April 12 it was 0.40 magn., and on 
May 6 and 7 it was imperceptible and appar- 
ently less than 0.1 magn. 
¢ EDWARD C. PICKERING. 
HARVARD COLLEGE OBSERY- 
ATORY, May 8. 
A SIMPLE OSMOMETER. 
THE end of a thistle tube is drawn out, broken 
off and closed temporarily with wax. The bulb 
is then filled with molasses and a piece of pig’s 
bladder,* is securely but loosely tied over the 
mouth. The wax is removed from the end of 
the stem and the end well fused. Two thick- 
nesses of strong linen are tightly drawn and 
securely tied over the membrane to take the 
strain. The bulbis then placed in water, when 
in a few minutes the column of liquid becomes 
higher and the air column compressed by the 
osmotic action through the membrane. 
In two or three days the maximum pressure 
is obtained, then the length of the air column 
is taken. The air in the stem is allowed to 
* These bladders may be obtained of Kny-Scheerer 
Co., 19th street and 4th Avenue, New York City. 
They are clean and dry like parchment, and cost ten 
cents each or one dollar per dozen. 
SCIENCE. 
791 
expand to its normal condition by puncturing 
the membrane with a needle and the length of 
the air column measured ; which length, divided 
by the length under compression, gives the 
pressure in atmospheres. 
The greatest pressure I have yet obtained 
with an apparatus of this sort is the expansion 
of 1.5 cm. to 13.2 cm., showing a pressure of 8.8 
atmospheres, or 668.8 cm. of mercury, or 129 
pounds per square inch. 
The highest pressure I find recorded for 
Pfeffer’s cell is 436.8 cm. mercury.* 
The air column after expanding will not be 
so long by six to eight per cent. as it was before 
compression, showing that some of the air has 
been absorbed by the liquid. 
The accompanying figure will serve to show 
how the apparatus is arranged. 
EK. HE. Bogue. 
LABORATORY OF PHYSIOLOGICAL BOTANY, 
HARVARD UNIVERSITY, April 16, 1901. 
CURRENT NOTES ON PHYSIOGEAPHY. 
PHYSICAL GEOGRAPHY OF THE TEXAS REGION. 
THE third folio of the Topographic Atlas of 
the United States is entitled ‘ Physical Geog- 
raphy of the Texas Region’ by Hill. It may 
well serve as a type of many to follow. Twelve 
folio pages are given to text, chiefly concerned 
with an explanation of relief and drainage ; 
then follow a sheet of nine climatic and other 
diagrams, four sheets holding 22 photographic 
views of typical landscapes, five sheets pre- 
senting 24 small topographic maps of typical 
reliefs and streams, and finally a folded map of 
Texas drawn under Hill’s direction by Selden 
and Johnson on a scale of 25 miles to an inch 
with contours every 250 feet. The imperial 
area of the ‘Texas region’ is indicated by the 
statement that each of more than twenty 
physiographic subdivisions has an extent equal 
to that of an average State. Mountains, pla- 
teaus and plains, canyons, valleys and waste- 
floored basins (bolsones) are described in so 
great variety that selection for special remark 
is difficult. Descriptions are marked by a 
thorough-going adoption of explanatory meth- 
ods, such as have always found ardent ad- 
* Goodale’s ‘ Physiological Botany,’ Vol. II., p. 229. 
