1895. ] NEW YORK ACADEMY OF SCIENCES. 27 
basal portion of the limestone, the whole will, most probably, 
prove to be Carboniferous. 
Dr. Reid notes the occurrence locally of white, coarsely crys- 
talline marble in considerable force at the upper end of Glacier 
Bay. Vein fillings of this charater occur at intervals in the 
argillites and with more frequency in the limestone, but it is 
possible that these greater masses noted by him may have re- 
sulted from contact metamorphism, as they lie in close proximity 
to the quartz-diorite. The specimens collected show no contact 
minerals, however. 
The Quartz-diorite.*«—As may be seen from the map this 
rock has a wide distribution in the vicinity. It is quite homo- 
geneous throughout, consisting of white plagioclase, somewhat 
dull and opaque from decomposition, with frequent thin prisms 
of hornblende and occasional biotites, and some quartz, the 
feldspar forming more than one-half the mass and giving it a 
predominantly white color, by means of which it may be unfail- 
ingly recognized at a distance. The only recorded observation 
on its contact relations is that by the writer made in 1890.+ 
The observed contact was with the argillites, and while the con- 
ditions under which it was made were by no means ideal, the 
contact seemed clearly an irruptive one. Furthermore, the areal 
distribution of this rock along the upper end of Glacier Bay, as 
mapped by Dr. Reid, seems to show that there its contact with 
the limestone is that of an intrusion, and that the white crystal- 
line marble reported there by him may be a phase of the lime- 
stone due to contact metamorphism. 
One further indication of the order of events in the vicinity is 
furnished by what seem to be apophysz from the quartz- 
diorite, which are found cutting the clastic rocks at some dis- 
tance from the main intrusion. Three such were noted by the 
writer in 1890, all of which were several yards in width, no 
accurate measurements being permissible at the time. They 
differ slightly from the main mass in appearance, and also carry 
pyrite in notable quantity, but in thin section are scarcely to be 
distinguished. They possess the same coarsely hypidiomorphic 
granular texture, with no variation between the centre and the 
sides, so far as could be noted, indicating a rate of cooling such 
as to make it probable that the enclosing rocks themselves had 
a high temperature at the time of the injection of these relatively 
small masses, one of which is more than twelve miles distant 
from the nearest outcrop of the main intrusion. 
*G. H. Williams, Nat. Geog. Mag., Vol. IV., p. 67. 
+H. P. Cushing, Nat. Geog. Mag., Vol. IV., p. 61. 
