KEPORT OF THE SECRETARY. 83 



the Ui)i)er Ohio and the hypothetical effects of ice blockade; (5) the 

 more complete mappin<:f of the osars of Maine, together with a critical 

 stndy of their structure, character, and relation ; (0) a comparative study 

 of glaciated and unglaciated Archaean knobs which occupy an isolated 

 position in the Silurian district of Central Wisconsin, and (7) a study of 

 the northern border of the Missouri Valley loess and its relation to other 

 members of the Quaternary series, as well as to altitude, topographic 

 features, and drainage systems. 



The tracing of the boundary of the drift and loess was undertaken by 

 Professor Chamberlin in person. The limit of the drift will be indi- 

 cated in a manner by the statement that his examination carried him 

 across Northeastern Illinois, Southern Iowa, Southeastern and Central 

 IS'ebraska, as far west as Denver, Colo., thence into the Valley of the 

 Arkansas southward across Indian Territory to Northern Texas, and 

 thence eastward across the northern part of Louisiana to the flood- 

 plains of the Mississippi, and from this point northward through West- 

 ern Tennessee, Kentucky, and Eastern Missouri. The results of the in- 

 vestigations of Professor Chamberlin and his assistants will appear 

 from time to time in the form of monographs and bulletins. 



Lake Superior District. — Office work in connection with the investiga- 

 tions of this division occupied the time of Prof. R. D. Irving and his 

 assistants until the weather permitted field exploration, which was at 

 once taken up and continued until nearly the close of the calendar year. 

 Professor Irving's line of research lies mainly in the Cambrian and 

 Archaean formations of the Lake Superior region. The assistants under 

 his direction were employed in the following fields : One was sent to 

 study the gneisses and granites of the Minnesota Valley, the results to bo 

 used, in connection with data obtained last season, in preparing a bul- 

 letin on the gneisses and granites of Central Mmnesota ; another was 

 sent to the Gogebic Lake country of the northern peninsula of Mich- 

 igan for the purpose of connecting the Huroniau of the Penokee region 

 of Wisconsin with that of the Marquette and Menominee regions of 

 Michigan ; a third continued the studies previously made in the region 

 of the national boundary line in the vicinity of Knife Lake, Mmne 

 sota — the object of the investigations being to determine the rela- 

 tion between the flat lying Animikie and the more northerly folded 

 schists; a fourth assistant was assigned a large area stretching from 

 Vermilion Lake, Minnesota, northeastwardly to its juncture with the 

 region in which the party just referred to operated, while for himself 

 Professor Irving reserved the necessary supervision of his subordinate 

 parties; a special study of portions of the Marquette region hitherto 

 unexplored, and a further examination of the exposures along the 

 national boundary-line, in the neighborhood of the Lake of the Woods. 

 The various i)arties had about com])leted the tasks assigned them and 

 returned to the Madison office for the purpose of elaborating the results 

 of this successful field season, when they had the misfortune to lose. 



