Three other shafts of the Tamarack Company, and three of the neighbouring Calumet and Hecla mine, have depths of between 4000 and 5000 ft.
Thenceforward he became a specialist in marine ichthyology, but devoted much time to the investigation, superintendence and exploitation of mines, being superintendent of the Calumet and Hecla copper mines, Lake Superior, from 1866 to 1869, and afterwards, as a stockholder, acquiring a fortune, out of which he gave to Harvard, for the museum of comparative zoology and other purposes, some $500,000.
The Calumet and Hecla mine, in the central part of that peninsula, is probably the most profitable copper mine in the world; up to 1909 it had paid about $107,850,000 in dividends.
That part of the city along the lake, known as Indiana Harbor, dates from 1901 and has grown very rapidly because of its position at the southernmost part of the Calumet District, and because of the meeting here of railway and lake commerce.
A good harbour has been constructed, a new ship canal connecting the harbour with the Calumet river.
Of these the largest is Lake Winnebago, between Calumet, Outagamie, Fond du Lac and Winnebago counties, with an extreme length of 30 m.
The civilized Brotherton and Stockbridge Indians live principally in Calumet county.