phere > 
EARLIER WRITERS. 5 
lowing geologists as having written more or less copiously upon this 
subject, the dates of the first and last publications being added in each 
case: Bigsby, 1824-1852; Bayfield, 1829; Houghton, 1831-1844; Jackson, 
1845-1869; Hubbard, 1846-1850; Logan, 1846-1866; D. D. Owen, 
1847-1852; Foster and Whitney, 1849-1861; Louis Agassiz, 1850-1%59; 
Marcou, 1850-1859; Norwood, 1852; Whittlesey, 1852-1877; Rivot, 
1855-1856; Hunt, 1861-1878; Macfarlane, 1866-1869; Alexander Agas- 
siz, 18677 Bell, 1869-1875; Pumpelly, 1872-1880; Marvine, 1873; Brooks, 
1873-1876; Rominger, 1873-1876; Irving, 1874-1880; Sweet, 1875-1880; 
Chamberlin and Strong, 1880; N. H. Winchell, 1879-1881; and Wads- 
worth, 1880. The preparation of anything like a satisfactory account of 
the explorations upon which the numerous writings of these geologists have 
been based, or of the writings themselves, would have taken away more 
time than I could afford to lose from the original studies necessary to my 
own work, and I therefore have not attempted it. 
I have, of course, familiarized myself with these writings, but the pro- 
portion of them from which I have drawn facts for incorporation into this 
memoir is a small one. I name them here in order of time of publication: 
J. W. Foster’s and J. D. Whitney’s joint ‘“‘Report on the Geology and 
Topography of a Portion of the Lake Superior Land District in the State 
of Michigan, Part I, Copper Lands,” made to the Commissioner of the Gen- 
eral Land Office, 1850; Sir W. E. Logan’s ‘Geology of Canada,” 1863; 
Thomas Macfarlane’s, ‘Report on Lake Superior,” in the Report of Prog- 
ress of the Geological Survey of Canada for 186366; the same gentle- 
man’s paper “On the Geology and Silver Ore of Wood’s Location, ‘Thunder 
Cape, Lake Superior,” published in the Canadian Naturalist for 1869; 
Robert Bell’s reports on the regions north and east of Lake Superior, 
published in the Report of Progress of the Geological Survey of Canada 
for the years 186669, 187071, and 1872—73; the report of R. Pumpelly 
and A. R. Marvine on the copper-bearing rocks of Keweenaw Point, in 
the Geological Survey of Michigan, Vol. I, 1869-73, Part IT; R. Pum- 
pelly’s paper on the “‘Metasomatic Development of the Copper-Bearing 
Rocks of Lake Superior,” published in the Proceedings of the American 
Academy of Arts and Sciences, Vol. XIII, p. 268, 1878, and “Lithology 
