BRIEFER ARTICLES 
A SIMPLE REVOLVING TABLE FOR STANDARDIZING 
POROUS CUP ATMOMETERS 
(WITH ONE FIGURE) 
In connection with field work carried on during the past season the 
writer has had occasion to standardize nearly 70 porous cup atmometers 
of the type described by Lirvincston.t The necessity of exposing the 
various cups in a series to uniform atmospheric conditions during the 
standardizing process is readily comprehended, but the difficulty in 
securing such conditions can be fully appreciated only by those who 
have tried it. Livincston has recently described a rotating table for 
standardizing these instruments,? and so far as fulfilling the requirements 
is concerned this can scarcely be improved upon. The only objection 
to it is the amount of time and expense involved in its construction, 
an objection which may have considerable weight if what is needed is 
a makeshift contrivance for temporary or perhaps occasional use rather 
than a durable piece of permanent equipment. The writer has devised 
for his purpose a very simple type of revolving table which can be 
constructed from readily obtainable materials with very little labor 
and expense and which has proven very serviceable. 
This apparatus is shown in the accompanying photograph (fig. 1). 
It consists, in brief, of the front wheel of a bicycle suspended horizon- 
tally within a wooden framework; on the upper side of the wheel is 
laid a piece of thick cardboard, or pulpboard, to support the bottles; 
from the lower side of the wheel wooden vanes are hung perpendicularly; 
the wheel is then caused to rotate by means of an air current from an 
electric fan. For constructing the framework three-quarter inch pine 
. board is sufficiently heavy, and rigidity is insured by the use of braces 
at the angles; the dimensions are largely a matter of convenience and 
will naturally depend somewhat on the diameter of the wheel used, 
height of atmometers, size of vanes, etc.; the framework shown in the 
figure measures 36X 30X24 inches (inside height, inside width, and 
depth, respectively). For supporting the wheel two upright pieces are 
* Carnegie Institution of Washington, Publication No. 50. 1906. 
?Plant World 15: 157-162. 1912. 
249] [Botanical Gazette, vol. 55 
