18 The American Geologist. juiy, i8ii7 
defined, and their practical importance easy to estimate. 
When, on the other hand, the ore development is a terminal 
one, disclosed only upon the edge, and enclosed between erup- 
tive m.iterial and disrupted masses of limestone tilted at high 
angles, little indication is afforded of the shape and size of 
ore bodies. Such an attitude is generally in a bol(J escarpment 
sometimes inaccessible above the immediate base. One of the 
ore bodies of this description on Texada, is exceptionally weil 
exhibited — in part by excavation. These remarks also apply 
to developments of ore in connection with terminal outcrops 
of limestone in a dioritic environment on the north side of 
Redonda island, and again to similar ones on the slope 
of Broughton peak, at the head of Barclay sound. A re- 
markable occurrence of an ore body near the mouth of the 
Serita river, at the head of another bay of the same inlet, 
affords a fine example of partial but still extensive replace- 
ment of limestone, around nuclei or cores of that material, as 
distinctly seen both at the end and on the slope of the eleva- 
tion near the surface of which the alteration has taken place. 
Some of these occurrences will now be described. 
Texada Island, Strait of Georgia. The old operations of 
the Puget Sound Iron Company of San Francisco aiford satis- 
factory exposures of the separate conditions under which mag- 
netic iron-ore of both modes of epigenesis occurs. Quarrj^ 
workings extend at intervals from the south side of the island 
about three miles, northwest from Gillies bay, following a sin- 
gle slope rounding a lofty summit of syenite at a general ele- 
vation of about 450 feet. On the range of the ore belt how- 
ever the slope is more or less broken into hills by erosion. 
Ore bodies within compass of tlie limestone belt are approx- 
ifnately lenticular in shape. All have been exposed to sub- 
aerial erosion, only so much of each development having been 
preserved as fell behind the eroded surface of the mountain 
side. In the several workings cores of marble are visible, cor- 
responding to unaltered interior or liether parts of ore bodies, 
left standing after excavation of the ore. 
Within compass of the epidotic rock the development of 
magnetite has been less regular, and less in concrete form, 
and the replacement or alteration less complete, the epigene 
product being a mixture of magnetite and epidotic material 
