In Memoriam . 
485 
criticism, which even threatened the existence of the survey, later, a 
sullen acquiescence in the truth, and finally, an admiration for the 
correctness and the courage of the position taken and a diversion of 
enterprise from unprofitable into successful lines of exploitation. In 
the second and third years of the survey Professor Irving’s field em¬ 
braced the Paleozoic and Archaean strata of central Wisconsin. In the 
last years he returned to the Lake Superior field and laid the broader 
foundation upon which nearly all of his subsequent investigations were 
based. The results of his studies in this official relationship are re¬ 
corded in the four volumes of the Reports of the Wisconsin Geological 
Survey (1873-1879). Meanwhile he had published several short articles 
in the American Journal of Science, the Transactions of the Wisconsin 
Academy, and elsewhere. Among these the more important are the “Age 
of the Copper-Bearing Rocks of Lake Superior and the Westward Con¬ 
tinuation of the Lake Superior Synclinal.’'* * * § “ Some New Points in the 
Elementary Stratification of the Primordial and Cambrian Rocks of 
South Central Wisconsin.”! “ The Stratigraphy of the Huronian Series 
of Northern Wisconsin, and on the Equivalency of the Huronian of the 
Marquette and Penokee Districts.” J 
In 1880 Professor Irving began those investigations upon the geology 
of the Lake Superior region for the United States government which 
continued until the time of his death. The first of these consisted of 
a comprehensive study of the copper-bearing series, the results of which 
he gathered into a monograph which perhaps stands as the best single 
expression of his work. § This was the first approach to a unified and 
systematic discussion of this great formation occupying a tract of 40,000 
square miles and embracing portions of Michigan, Wisconsin, Minnesota 
and Canada. Whatever differences of opinion may continue to exist 
concerning the interpretation of the debated phenomena, this must 
ever be recognized as a monument of industrious and able investigation 
and of candid and careful induction. Following these studies upon 
the copper-bearing series, Professor Irving took up in a correspond¬ 
ingly comprehensive manner, the investigation of the iron-bearing for¬ 
mations of the Lake Superior region and their correlation with each 
other and with the original Huronian of Canada. Upon this work he 
was engaged at the time of his death. He had in preparation and 
nearing completion a monograph upon the Penokee-Gogebic range and 
had well in hand a large amount of material relating to the Marquette, 
Menominee and Vermilion Lake series, as well as the original Huronian 
and Animike groups. His loss at this fruitful stage of his work, incal- 
* Am. Jour. Sci., Vol. VIII, Art. vii, p. 46, 1874. 
t Am. Jour. Sci., Vol. IX, Art. vii, p 440, 1875. 
t Am. Jour. Sci., Vol. XVII, Art. xlix, p. 393, 1879. 
§ “ Copper-Bearing Rocks of Lake Superior.” Monograph V., U. S. Geol. Survey, 1883. 
