W. A. Norton — Variability of the Ultimate Molecule. 185 
several hours. As a final result the set subsides entirely, or 
settles into a permanent value; according to the amount and 
duration of the stress applied. 
These facts lead unmistakably to the conclusion that the 
molecules of the materials rin ates on, as a result of the 
rium. To make this more evident, let us consider somewhat in 
detail the results of a single series of experiments; for example, 
those made by Captain Rodman (U. 8. Army) on a cylinder of 
cast iron, 35 inches long and 1°366 inches in diameter, subjected 
to a tensile stress. The smallest set observed was +;7'535 of 
the length, and resulted from the temporary Rte ip of a 
i 1 This stress, 
temporarily applied, had then the effect to produce an abiding 
increase of +;;'s35 in the distance between two contiguous 
molecules in the line of stress. Loads increasing by 1, 
pounds, from 6,000 pounds to 25,000 pounds per square ane 
. : 
cules which, whenever no external stress was in actual opera- 
tion, must have been in equilibrium under the operation of 
antagonistic forces of attraction and repulsion exerted by the 
molecules, and yet as the result of a temporary application of a 
series of increasing loads, twenty in number, it up 2 
of as many different configurations, in which the distance be- 
tween contiguous molecules in the line of stress augmente 
progressively from tO gis} and this although the actual 
displacements snécitaes by the suspended loads were only from 
