Four Views of the Burlington Diamond (a little over two carats); enlarged about three diameters.
(Owned by Bunde and Upmeyer, Milwaukee.)
Not only did the ice mantle register its advance in the great ridge of morainic material which we know as the "kettle moraine," but it has engraved upon the ledges of rock over which it has ridden, in a simple language of lines and grooves, the direction of its movement, after first having planed away the disintegrated portions of the rock to secure a smooth and lasting surface. As the same ledges have been overridden more than once, and at intervals widely separated, they are often found, palimpsestlike, with recent characters superimposed upon earlier, partly effaced, and nearly illegible ones. Many of the scattered leaves of this record have, however, been copied by geologists, and the autobiography of the ice is now read from maps which give the direction of its flow, and allow the motion of the ice as a whole, as well as that of each of its parts, to be satisfactorily studied. Recent studies by Canadian geologists have shown that one of the highest summits of the ice cap must have been located some distance west of Hudson Bay, and that another, the one which glaciated the lake region, was in Labrador, to the east of the same body of water. From these points the ice moved in spreading fans both northward toward the Arctic Ocean and southward toward the States, and always approached the margins at the moraines in a direction at right angles to their extent. Thus the rock material transported by the ice was spread out in a great fan, which constantly extended its boundaries as it advanced.
The evidence from the Oregon, Eagle, and Kohlsville stones, which were located on the moraine of the Green Bay glacier, is that their home, in case they had a common one, is between the northeastern corner of the State of Wisconsin and the eastern summit of the ice mantle—a narrow strip of country of great extent, but yet a first approximation of the greatest value. If we assume, further, that the Saukville, Burlington, and Dowagiac stones, which were found on the moraine of the Lake Michigan glacier, have the same derivation, their common home may confidently be placed as far to the northeast as the wilderness beyond the Great Lakes, since the Green Bay and Lake Michigan glaciers coalesced in that region. The small stones found at Plum Creek, Wisconsin, and the Cincinnati stone, if the locations of their discovery be taken into consideration, still further circumscribe the diamond's home territory, since the lobes of the ice mass which transported them made a complete junction with the Green Bay and Lake Michigan lobes or glaciers considerably farther to the northward than the point of union of the latter glaciers themselves.
Three Views of a Lead Cast of the Milford Stone (six carats); enlarged about three diameters.
We are indebted to the courtesy of Prof. T. H. Norton, of the University of Cincinnati, for the above illustrations.
If, therefore, it is assumed that all the stones which have been found have a common origin, the conclusion is inevitable that the ancestral home must be in the wilderness of Canada between the points where the several tracks marking their migrations converge upon one another, and the former summit of the ice sheet. The broader the "fan" of their distribution, the nearer to the latter must the point be located.
It is by no means improbable that when the barren territory about Hudson Bay is thoroughly explored a region for profitable diamond mining may be revealed, but in the meantime we may be sure that individual stones will occasionally be found in the new American homes into which they were imported long before the days of tariffs and ports of entry. Mother Nature, not content with lavishing upon our favored nation the boundless treasures locked up in her mountains, has robbed the territory of our Canadian cousins of the rich soils which she has unloaded upon our lake States, and of the diamonds with which she has sowed them.
