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THE POPULAR SCIENCE MONTHLY. 



a discontinuous current, and, although the 

 instrument is capable of showing the vari- 

 ations of a continuous current, the author 

 did not have this application in mind when 

 he constructed it. No patent was taken out 

 for the device, for the inventor believed 

 that " a scientific man should place no re- 

 strictions upon his work which would tend 

 to prevent the repetition of an experiment 

 of scientific interest. A full description 

 should have been published. This was at 

 first delayed, from the pressure of other 

 work, and lack of appreciation of the im- 

 portance of the results. Afterward I was 

 unwilling to enter into a controversy, or to 

 obstruct my friends, who were struggling to 

 obtain proper recognition of the great re- 

 sults they had obtained in the same field." 



What Ice can do# The important part 

 in producing or modifying topography that 

 has hitherto been conceded to moving mass- 

 es of ice has recently been disputed by some 

 American geologists, who have denied that 

 ice possesses any eroding or excavating pow- 

 er. Professor J. S. Newberry has published 

 an article sustaining the old theory against 

 these contradictions by evidences drawn from 

 the visible action of living glaciers, as in the 

 Alps, and also in the mountains of Oregon, 

 where a remarkable monotony of surface 

 has been produced by ice-action. The crest 

 of the Cascades, crowned by the volcanic 

 peaks, Mount Jefferson, Mount Hood, etc., 

 has sides sloping east and west, like the roof 

 of a house. These slopes are planed down, 

 and their asperities removed, everywhere 

 showing the effects of a powerful grinding 

 agent. In the Laurentian belt north of the 

 lakes, where were formerly high mountains, 

 are now only low hills and rolling surfaces, 

 and the strata are " standing at high angles 

 but planed down, scratched and ground by 

 glaciers, until their cut edges are like boards 

 in a floor." Similar work has been performed 

 between the Hudson and the Connecticut. 

 The action of running water on topography 

 is not only different from that of ice, but 

 antagonistic to it. Water deepens the 

 lines of drainage and increases the asperi- 

 ties. The canons of the Colorado are typi- 

 cal and characteristic illustrations of water- 

 action on continental surfaces. Great ice- 

 sheets, on the contrary, tend to reduce all 



asperities, fill depressions, and render the 

 topography monotonous. If ice is compe- 

 tent to do the work of shaving and smooth- 

 ing the landscape, which the author aims to 

 prove by his citations that it has done, much 

 more may it have excavated lake -basins. 

 " The power which has done the greater is 

 certainly equal to the less." Probably, Pro- 

 fessor Newberry adds, some misapprehen- 

 sion arises from an inadequate conception 

 of the composition and action of a glacier. 

 " It is, perhaps, regarded as a mass of pure 

 ice, which by itself would have little grind- 

 ing power ; but a glacier is a great moving 

 mass which by its weight and motion crush- 

 es and removes all but the most solid rock 

 prominences over which it passes. Where 

 it impinges against cliffs, these are some- 

 times lifted, and huge blocks are carried 

 away. In many localities we find stones 

 hundreds of tons in weight, which have 

 been torn from their beds and carried many 

 miles. Pure ice, then, in sufficient volume 

 is a potent and almost irresistible agent of 

 erosion, quite independent of its grinding 

 action ; but, as a matter of fact, all glaciers 

 are studded below with rock - fragments, 

 great or small, which they have torn up in 

 their course ; so that sand, gravel, and 

 bowlders constitute a coating to the under 

 surface of a glacier which may be compared 

 with the emery on a copper wheel." 



Have we gone too far in draining 

 Swamps ? In one of a series of papers on 

 " The Proper Value and Management of 

 Government Timber-Lands," read at the De- 

 partment of Agriculture, in May last, Mr. 

 M. C. Read showed that harm rather than 

 good has been done by the draining of the 

 swamps which has been so vigorously pros- 

 ecuted during the last twenty-five years. 

 The swamps were constant store-beds and 

 sources of moisture, and tended to keep the 

 streams that drew upon them at an even 

 level. In draining them, they being generally 

 found on the same level as the surface of 

 adjacent lakes, the outlets of the lakes were 

 deepened so that they could be drained 

 more speedily and completely. To accom- 

 modate the more rapid outflow that accrued, 

 the streams below were often straightened 

 and cleared out, and the rapid concentration 

 of the water into the larger streams was 



