1918] 
DUGGAR AND BONNS—RATE OF TRANSPIRATION 155 
the central axis, each plant was made to turn upon the axis 
of its own platform. 
The construction of the table was as follows: 
A heavy cast-iron base, 5 inches in diameter and 34 inches 
high, with a footing 12 inches in diameter and 14 inches thick, 
supported a polished steel shaft of l-inch diameter, 4 feet 
long. Four inches of this shaft were sunk into the top of the 
base, which had a small shoulder. On this shoulder rested a 
collar or ring enclosing a set of ball bearings which was 
slipped over the shaft, these carrying the greater part of the 
weight of the revolving system. 
The 8 arms carrying the plant platforms consisted of 
1X1ł-inch channel irons, 4 feet long, arranged radially and 
bolted each with 2 bolts to a central plate 10 inches in diam- 
eter. This central plate was screwed to a short collar or 
outer shaft of iron tubing of %¢-inch thickness which slipped 
easily over the supporting steel central shaft without exces- 
sive play. On the portion of the collar below the central 
plate was bolted a sprocket wheel 84 inches in diameter. The 
collar extended a little more than 1 inch above the central 
plate. Above this collar was imposed another short collar 
which was firmly screwed with set screws to the central steel 
shaft and did not bear upon any of the parts below; a sprocket 
wheel 3 inches in diameter was bolted to this second collar 
and a second ring of ball bearings fitted over the latter. On 
this ring then rested the second outer shaft, which revolved 
freely over the main steel axis, and extended a short distance 
above it. 
The plant platforms consisted of dises of seasoned wood 
3 inch thick and 7 inches in diameter. To the bottom of each 
was screwed a brass sprocket wheel 24 inches in diameter. 
Each of such sprockets fitted over a cylindrical steel plug & 
inch in diameter, projecting } inch above the top of a rec- 
tangular cast-iron sleeve which slid along the channel iron. 
The platform could thus be set at any point along the arm, 
and was fixed by a set screw in one side of the sleeve. 
Guy wires connected by steel eyelets from the upper end 
of the outer revolving shaft to an eyelet set in each channel 
