156 



itCIENCE. 



[N. S. Vol. XI. No. 265. 



highland or mountain region, for its rocks are 

 of deformed structure or of deep-seated habit 

 over large areas. During the long period of 

 combined sub-aerial and marine attack upon 

 the highland, large rivers must have cut down 

 deep valleys, while sea waves abraded a plane 

 around its literal margin ; that is, the valley, 

 CEF, would have been eroded, while the mar- 

 ginal plane, AF, was abraded. In the time 

 needed to give AF a breadth of several miles, 

 the main valley, EF, would be reduced to very 



m<g»- ///Az- fff^^^y^ ^»c 



gentle slope. Under the supposition that the 

 surface attacked by the encroaching sea was of 

 such a relief that a considerable subsidence 

 might occur during its submergence, the valley, 

 FE, would in time be buried by the sediments, 

 ADK. No buried valleys are known in the 

 even sub-Cambrian floor. Their absence can 

 be explained only under the supposition that 

 the sea abraded the land to a greater depth 

 than the valleys had been cut in it, and hence 

 that but moderate subsidence occurred during 

 abrasion. Under this limiting condition, ex- 

 tensive peneplanation must have occurred be- 

 fore great marine encroachment by abrasion 

 could have been accomplished. 



THE URAL MOUNTAINS. 



The excursion of the International Geological 

 Congress to the Ural Mountains in 1897 gave 

 Dr. F. P. Gulliver opportunity for reaching the 

 following conclusions regarding the evolution 

 of their existihg form. A long period of sub- 

 aerial planation, probably aided by marginal 

 marine action, reduced the region to a lowland 

 surmounted by a few monadnocks. The low- 

 land was then arched by successive uplifts, the 

 axes of greatest elevation being east of the 

 middle of the range ; and benched valleys were 

 eroded beneath the general upland level. 



Approaching the range from the west, there 

 is a gradual transition from the great Russian 

 planes of nearly horizontal structure to the dis- 

 sected peneplain of deformed structures. Ap- 



proaching from the east, a part of the old 

 mountain peneplain remains at moderate alti- 

 tude adjoining the Siberian Tertiary plains ; 

 unexplained lakes occur in this part of the 

 peneplain, which is generally separated from 

 the revived mountains on the west by an abrupt 

 ascent, thought to be a weathered fault scarp 

 {Bull. Geol. Soc. Amer., X., 1899, 69-82). 



W. M. Davis. 



NOTES ON TERRESTRIAL 3IAQNETISM* 



Captain Denholm Feaseb, R.E., is at pres- 

 ent engaged in making the necessary arrange- 

 ments for inaugurating a magnetic survey of 

 India and Burma. 



Captain Lyons, E.E., in charge of Geolog- 

 ical Survey of Egypt, has for some years been 

 making magnetic observations during his jour- 

 neys in vai-ious parts of Egypt. It is hoped 

 that before long a systematic magnetic survey 

 of Egypt can be undertaken. 



Two proposed sites for the Standard Mag- 

 netic Observatory in the vicinity of Washington 

 have been examined during the past month by 

 magnetic parties under Dr. Bauer's direction, 

 in order to determine the most suitable place. 

 One of these sites, situated twenty-two miles to 

 the northwest of Washington, has revealed 

 pronounced magnetic anomalies, while the 

 other site, sixteen miles to the southeast of 

 Washington, has thus far shown no abnormal 

 values. The latter site appears to be also a 

 favorable one as far as freedom from electric 

 tramway influence is concerned. 



There are at present four observatories at 

 mining stations in Germany, at which the varia- 

 tions of the magnetic declination are being con- 

 tinuously recorded by photographic means, viz. : 



1. Clausthal, Harz. This observatory has been in 

 existence since the days of Gaiiss. It is provided -with 

 a Gaussian declinometer for eye-readings, and a more 

 modern instrument for self-registering purposes. 

 Copies of the daily records can be had upon applica- 

 tion. 



2. Beuthen, Upper Silesia. 



3. Bochum, Westphalia. 



4. Hermsdort, bei Waldenburg. 



The last three-named stations were started at 

 * From advanced sheets of Terrestrial Magnetism. 



