DIAMOND FIELD OF THE GREAT LAKES 383 



Upham, 1 Low, 2 Mclnness, 3 and Bell. 4 In the Ohio area and in 

 some others where a large number of observations of striae have 

 been collected the scale of the map has made it necessary to 

 generalize, but these regions have been so carefully studied, both 

 as regards moraines and scorings, that it was found easy to do 

 this. In fact, within the territory of the United States the data 

 at hand are sufficient for a fairly satisfactory plotting of the gen- 

 eral direction of glacial movement at almost every point. Within 

 the domain of Canada the great wilderness region has been 

 covered only by reconnoissance surveys and except in the territory 

 bordering on the lakes there exist only a few scattered obser- 

 vations from which to construct a map of glacial movement. In 

 the district to the southeast of James Bay some surveys have been 

 made but the material is not yet in print. In the region south- 

 west and west of James Bay, which possesses also great inter- 

 est, no data are available. Particularly in this latter region it is 

 likety that striations will be found corresponding to different peri- 

 ods, owing to the fact that the ice from the Keewatin and Labra- 

 dorean ?ieves coalesced within this territory. 



By plotting the diamond localities on the map it is seen that 

 all but the Plum Creek locality are situated on the moraines of 

 the later ice invasion, and that the latter locality is quite near to 

 the moraine, within the area of overwash. It is also worthy of 

 note that all but the Dowagiac stone were found in one of the 

 marginal moraines which marked the greatest advance of the ice 

 during its later invasion. The moraine which passes through 

 Dowagiac corresponds to a somewhat later period, during the final 

 retreat of the ice. 



1 Warren Upham : Late Glacial or Cbamplain Subsidence and Re-elevation of 

 the St. Lawrence River Basin, Am. Jour. Sci. (3), Vol. XLIX, 1895, pp. 1-18. 

 PI. I. 



2 A. P. Low: Report on Exploration in the Labrador Peninsula, Geol. Surv. 

 Can., Vol. VIII, 1896, Rept. L, p. 387, Sheets Nos. 585-588. 



3\V. C. McInness: Sixth Report, Bureau of Mines, Ontario, 1S96, Sheet No. 9. 



^Robert Bell: Report on the Geology of the French River Sheet, Ontario, 

 Geol. Surv. Can., Vol. IX, 1898, Rept. I, pp. 29, Sheet No. 125. 



