26 TRANSACTIONS OF THE [oct. 28, 
accumulating at the bases of other mountains made up of the 
same material. 
3. Thin bands of black, graphitic slates with good slaty 
cleavage are interstratified with the foregoing varities. There 
seem to be several such bands, though their apparent number 
may be increased by faulting. 
Careful search for fossils was made in these rocks at several 
points by the writer, who had his labor for his pains. The series 
has great thickness, and may comprise rocks of more than one 
age, but is so homogeneous throughout that its study yields dis- 
appointing results. Its base was nowhere seen, but a vertical 
section of more than 3,000 feet is exposed on Mt. Wright and 
its outlying ridges aaieh rise from Muir inlet, just below the 
end of Muir elacier.* . 
4. The Glacier Bay Limestone.-—The mountains adjoining 
the larger part of Glacier Bay consist of dolomitic limestone of 
a dark color, and for the most part extremely pure, containing 
only a trace of insoluble matter. Like the argillite, it is meta- 
morphosed and cut up by joints, but the cracks, often widened 
considerably by solution, are without exception filled by crys- 
talline calcite, binding the whole into a firm mass and much re- 
tarding its disintegration. On the peaks east of Muir inlet the 
limestone may be seen capping the argillites, apparently con- 
formably. Its summit was nowhere seen, but it has an unmis- 
takable thickness of several thousand feet. It may conven- 
iently be designated the Glacier Bay limestone until such time 
as some other name may prove more appropriate. Fossils in 
this limestone are rare, and damaged by metamorphism. The 
writer found them in ‘place on Douglass Island in 1890, and in 
loose pieces elsewhere, but unfortunanely the recognizable 
forms gave no precise indication of the age. However, further 
light has been shed upon this point by the discovery, chronicled 
by Prof. Stevenson,} of a piece of fossil coral on one of the 
moraines of the Dirt glacier. A single one of the peaks, amid 
which the Dirt glacier has its source, is capped by the limestone; 
otherwise the drainage basin of this glacier lies entirely in ar- 
gillites or eruptive rocks, so that the locality whence this coral 
was derived is pointed out beyond question. Prof, H. 8. Wil- 
liams, in a letter to Dr. Reid, pronounces it a species of Lons- 
daleia and regards it as demonstrative of the Carboniferous age 
of the horizon whence it came. As this was apparently the 
* The areal geology of the region is delineated so far as may be, on the accompany- 
ing map, Plate I., at close. This map was prepared by Dr. Reid for another purpose, is 
based on his as yet unpublished material, and appears here through the courtesy of the 
Director of the United States Geological Survey and of Dr. Reid. 
+ J. J. Stevenson, Scot. Geog. Mag., Feb., 1893, p. 5. 
