February 6, 1914] 



SCIENCE 



209 



■of sea ice, taken from Captain Scott's narra- 

 tive of his South Pole expedition, which re- 

 calls the subject to mind. This picture seems 

 to afford a very decided support for the above 

 theory. 



I conceive that the conditions under which 

 eskers were formed were similar to those illus- 

 trated by this view of a pressure ridge, al- 

 though in this case the ridge is understood to 

 have been formed in ice resting on water. It 

 is possible that at the time of the formation of 

 the esker ridges the movement of the ice was 

 facilitated by water underlying the sheet over 

 considerable areas, so that the ice was partially 

 afloat at least for portions of each year. 



Very pronounced ridges of boulders and 

 other material are formed under weather con- 

 ditions now existing around the shores of 

 small interior lakes in cold climates by the 

 " push " of the ice that covers the lakes each 

 winter. 



I believe that the seasonal variations in 

 temperature that must have occurred even 

 during the low average temperature of the 

 glacial period, with resulting changes in the 

 internal structure and movements of the ice, 

 constituted an influence of more importance 

 in connection with general glacial phenomena 

 than has heretofore been recognized. 



The " trough " or depression along one or 

 both sides of the ridge which sometimes oc- 

 curs as a marked feature in connection with 

 an esker was probably due primarily to the 

 greater scooping and shoving effects of the ice 

 on the underlying earth material immediately 

 adjacent to the ridge, on account of the 

 broken condition of the ice and the increased 

 weight resulting from increased thickness and 

 the superimposed broken blocks and frag- 

 ments. The esker ridge itself and such side 

 depressions would sometimes determine or 

 materially modify the immediate post-glacial 

 drainage of the locality, when the depressions 

 would become still further emphasized by 

 stream erosion during and after the melting of 

 the ice. Furthermore, the " delta formation " 

 sometimes found near the end of the esker is 

 thus explained. 



A theory similar to the above is applicable 

 to certain irregular detached groups of knoUa 



or hum m ocks and short ridges with interven- 

 ing troughs and hoUows, called hame areas. 

 Some examples of these may mark a sort of 

 focus for the lateral shove from various di- 

 rections of the surrounding ice sheet. In at 

 least one locality that has been studied in con- 

 siderable detail the assumption of the forma- 

 tion of an interglacial ridge by a process sim- 

 ilar to that described above, but with a direc- 

 tion transverse to that of the general move- 

 ment of the ice sheet, seems to afford a clue to 

 an explanation of several surface features of 

 the vicinity, and possibly this may also apply 

 to some special eases where there has been 

 difficulty in fitting the terminal moraine 

 theory with entire satisfaction. 



The probability of an extensive ice sheet of 

 moderate thickness in comparison with that 

 of earlier ice " invasions " of the same area, 

 and as the final stage of the glacial period for 

 the region in question, suggests other interest- 

 ing deductions in connection with the causes 

 of present surface forms. John Millis 



November 25, 1913 



MATTER AND MEMORY 



On reading with interest the article of Pro- 

 fessor E. D. Carmiehael, Science, December 

 19, I find on page 869 a statement which can 

 not pass as entirely general: "... mind . . . 

 has chosen to assume that matter is without 

 memory." 



While in abstract reasoning we prefer to 

 assume that matter has no memory, neverthe- 

 less we well know that in all too many cases 

 this assumption is made for simplicity, not for 

 exactness. The existence of zero drift, per- 

 manent set, elastic, magnetic and dielectric 

 hysteresis, etc., so complicates the actual con- 

 ditions, by making them dependent on the pre- 

 vious experiences of the material under con- 

 sideration, that we can not set up ideally exact 

 general equations. The complications are by 

 no means as overwhelming as those, for exam- 

 ple, which present themselves in dealing with 

 warm-blooded animals, but they are real. 

 What the instrument-maker desires is matter 

 which does forget, whether he be interested in 

 galvanometer suspensions or transformer cores. 

 To speak figuratively, the suspension " re- 



