104 W. Mathews on Glacier-motion. 
consecutive years, of a series of points originally in a straight 
line, are plotted to scale. The diagram exhibits the very small 
motion of points close to the side, whence the curves extent 
with their concavity downward as far as the point of maximum — 
differential velocity, where they become convex, and gradually | 
increase in curvature up to about one-fourth of the width of the 
glacier, whence they sweep across to the corresponding point on — 
the opposite side in a curve so flattened as to be scarcely distin 
guishable from a straight line. Cr 
he above considerations lead to the following conclusions 
upon the five fundamental propositions of Canon Moseley. | 
1. It is probable that every molecule of a glacier moves Wilh 
a very slow differential motion, which, whenever the ice 1s co 
tinuous, is continuous from molecule to molecule, and fom 
moment to moment of time. : : 
2. The hypothesis that the differential motion 1s uniform 
. 
from center to side is wholly contrary to fact. The sea 
theory and fact greatly strengthens his position ; 
made good this part of his case. 
tions above described, to range for 
inch apart, and an interval of twenty-four hours, from 
to the 5,55 of an inch.* ; rents 
5. On the other hand, the slow continuous le gear 
the molecules of a glacier are undistinguishable in ee 
displacements of the molecules of an ice-plank, suppoh™ 
extremities and allowed to subside under the 10 uence 
weight, displacements which require for their eae 87 
have shown in the Philosophical Magazine for November 
a force considerably less than 1} Ib. per square inch“ 
fore, than the very force which the Sanit considers Suh. 
shear the Mer de Glace if it descends by its own grav" 
* This objection has been f in the Phil 
zine for July, 1870, een forcibly urged by Mr. Ball in 
actual glacier,—the latter having been shown, 1 of a 
