80 The American Geologist, August, 18G7 
store of native copper. In a letter to the editor of Sillinian's 
Journal, after noting a fifty-ton lump of copper, Jackson adds, 
"Those who were surprised that I recommended working mines 
for native copper, should come and see and they would believe." 
Important as were the economic results attained in this 
field by his labors, his views of the geological structure and of 
the succession, if properly understood at the present da}', are 
not in accord with the most recent results obtained in that 
field. Foster and Whitney succeeded to the work in the cop- 
per region. They set aside the theoretical work of Jackson, 
and in turn their views have been displaced by later investi- 
gators. Such has been the history of progress in other fields. 
In the reaction from the doctrine of Werner concerning the 
basaltic rocks, the geologists of the middle years of the cen- 
tury just closing were largely blind to the evidence of igneous 
rocks which were not intruded but spilled out over the sur- 
face in the. form of contemporary sheets. The enormous lava 
flows of the Keweenaw peninsula were regarded by Jackson 
as intrusive rocks capable of elevating the sandstones with 
which they are associated. It is only within recent years that 
the essential flow character of the trap masses in the upper 
portion of the Connecticut valley has been recognized. If 
Jackson nmde a mistake in this matter, he has had able com- 
pany in the years that have passed. The age of the red sand- 
stones on the north side of the penirisula still depends upon 
local evidence of unconformity. Jackson seems to have con- 
sidered the rocks of Triassic age, agreeing with Marcou: lat- 
er he expressed some doubt. Now the rocks are placed by the 
U. S. geological survey between the lower Cambrian and the 
Huronian. But Jackson in later years thought that our red 
sandstones might be of very different ages. It is not probable 
that he attached much importance to the question of age of 
the Lake Superior sandstones. There, as in New England, it 
was the economic geology which interested him mostly. 
Before passing from this phase of Dr. Jackson's work, it 
should be stated that he was appointed one of the state geol- 
ogists of New York by governor Marcy, but resigned. He had 
also been called upon in planning the work of that survey. 
Jackson's work as a state geologist came to an'end with the 
first half of the century. Thence forward we find no abate- 
