and its associates on Lake Superior. 249 
0. 19. ALBANY aND Boston AMyGpALomw.—The rock of 
this bed is a wholly irregular mixture of hard light-green 
amygdaloid and soft brown amygdaloid, in which the vesicular 
form is frequently lost from the fact that the cavities contain- 
ing secondary minerals have extended and become merged 
together, forming a confused patch and vein structure: 1, 
Prehnite, amorphous and altered to a slightly cavernous appear- 
ance on the surface—2, Quartz in pri , Orthoclase in 
minute crystals chiefly on the altered prehnite, with which its 
formation is probably connected, and also on the quartz, 
0, 20. Same BED.—On the amygdaloid, which contains 
quartz amygdules, lie: 1, Prehnite penetrated with strings and 
films of copper—2, riz in prisms; chlorite-like mineral in 
hemispherical forms, with radiating structure—Orthoclase in, 
minute crystals; all these lie separately on the prehnite—3d, 
Calcite covering all the above mentioned members. 
No. 21. Same Bep.—1, rtz, in prisms—2, Chlorite-like 
mineral in hemispherical forms, with radiating structure; 
Wherever it is in contact with the quartz it has pitted it and 
faten into it—8d, Calcite, : 
0. 22. SAME BED.—On the amygdaloid lie:—1, Prehnite 
crystals in reniform masses—2, eit in prisms on the 
Prehnite crystals—8, Orthoclase; Calcite; the orthoclase is in 
Minute crystals on the prehnite and quartz. __ : 
No. 23. Samu Bep.—The amygdaloid on which the following 
Succession occurs consists of quartz and chlorite, and is wholly 
altered—so much so that the quartz which now composes a 
large a of it is evidently of- the cates age as ae which fol- 
Ows the prehni rehnite, in © e reniform masses 
prehnite—1, Prehniite, eager 28 ior tral 
a. par crystals occur in the cavity thus formed as well as on 
'€ outer surface of the analcite. 
0. 26. Same sep.—l, Prehnite—2, Quarte—3, Copper, 
M threads often moulded to the quartz—4, Orthoclase in 
Minute crystals planted on the prehnite, quartz and copper. 
Am. Jour. Sct —Tarrp Serres, Vor. I, No. 10.—Ocr., 1871. 
17 
