Philadelphia Meeting ofGeological Society .— Upham. 101 
downward percolating waters. He urged the advantage of an explora¬ 
tory boring from the bottom of one of the copper mining shafts,*which 
might penetrate to a total depth of nearly 15,000 feet below the surface. 
Notes on Glaciers. Harry Fielding Reid, Baltimore, Md. 
1. The request made last year for observations on the ^advance or 
retreat of American glaciers has brought but few responses; these, 
however, show that the Carbon River and North Puyallup glaciers on 
Mt. Rainier, and the Illicellewaet glacier in the Selkirk mountains, are 
retreating. 
2. If we consider a glacier in equilibrium, the amount of ice flowing 
through any section in a year must equal the ice added to the glacier 
above that section in the same time. This, in connection with the fact 
that there is.actual accumulation in the reservoir and melting in the 
dissipator (the region below the n6ve line), shows that the flow must be 
greatest in the neighborhood of the neve line and must diminish as we 
ascend or descend the glacier from that region. This law of flow is 
exact, and it must replace the similar empirical rule of velocity first 
stated by Desor. It is inferred that the greatest flow in the ice-sheet 
of the Glacial period must have been near the n&ve line, and that this 
was probably much nearer to the outer edge of the sheet than to the 
center of distribution. In general, the velocity will be greatest where 
the flow is greatest. 
3. Consideration of the flow in a glacier of indefinite length resting 
on a bed of uniform slope leads to the conclusion that with ordinary 
glaciers the parts near the end must owe some of their motion to pres¬ 
sure from behind. This has been generally believed, but not clearly 
reasoned out. 
1. As a result of this pressure, there must be in the dissipator a 
motion of the ice away from the bed. In the reservoir, on the contrary, 
there is a motion toward the bed. We are enabled to draw approxi¬ 
mately the lines of flow followed by the ice from the time of its depos¬ 
ition as snow to the time of its melting, and also to show the positions 
occupied by the successive strata. 
5. If we knew the distribution of velocity and of melting, we could 
calculate the form of the glacier’s surface. The vertical or overhang¬ 
ing ends of some Greenland glaciers described by Prof. Chamberlin are 
due to the large quantity of debris in their lower layers, causing more 
rapid melting there. 
6. Glaciers are rarely in complete equilibrium with their surround¬ 
ings. The relations establishing the. form of the surface bring about a 
state of unstable equilibrium, and this would lead us to expect the 
great fluctuations in the extent of glaciers which we actually observe. 
[This paper will be published in full in the Journal of Geology.] 
It was discussed by Profs. G. Frederick Wright and R. D. Salis¬ 
bury, the latter noting that an upward tendency of the lamination of 
Greenland glaciers is observable where the border is thin but not where 
it is thick. 
