August 26, 1904.] 



SCIENCE. 



277 



This restraining influence of the bluffs is 

 brought out in the table. Below Vicksburg 

 the right-handed cutting is notably in ex- 

 cess. Here the number of cut-offs is likewise 

 in excess on the right side of the stream. A 

 typical case of restraint may be seen at 

 Natchez (Fig. 3), where the development 

 of the left-handed curve is hindered while 

 that on the right is free. As a result of 

 these conditions and the down-valley mi- 

 gration of the meanders the river has twice 

 cut through the neck of the lobe and is now 

 increasing the radius of its present curve 

 preparatory to a third cut-off. In stretches 

 which have nothing but free flood-plain on 

 both sides, a right-handed curve could not 

 develop without an accompanying left- 

 handed curve — a fact which can be more 

 readily appreciated when it is remembered 

 that, except for the down-valley movement 

 of the meander as a whole, the center of 

 the growing curve on the open flood-plain 

 is relatively fixed, and the extension and 

 development of sympathetic curves in ad- 

 jacent parts of the channel are necessary 

 attendants of the growth of the meander. 



The foregoing serves to show that on the 

 Mississippi, cut-offs as well as relative bank 

 cutting should be counted as right or left 

 not over the course as a whole but in sec- 

 tions which depend for their individuality, 

 in part at least, upon conditions external 

 to the river and not directly related to 

 deflective tendency. 



In conjunction with Professor M. S. W. 

 Jefferson, of the Michigan State Normal 

 College, the writer has undertaken meas- 

 urements of this kind in Michigan along 

 the River Rouge between its headwaters 

 and Detroit. The river flows to the east 

 through a plain of glacial and lacustrine 

 origin which, on account of its level nature, 

 offers advantages not possessed by the Mis- 

 sissippi. The latter stream, by cutting into 

 a bluff, on one side, and into flood-plain de- 

 posits, on the other, does not enable one to 



use the maps previously mentioned in de- 

 termining the absolute amount of work 

 accomplished ou the two sides of the 

 stream. The areal expression of such cut- 

 ting is no basis for the determination of the 

 actual amount performed. The river may 

 be doing even more work on the bluffs 

 along its eastern bank than it accomplishes 

 on the western bank. The River Rouge 

 has incised itself in a level plain and in 

 the process of deepening and widening its 

 vaUey swings against bluffs of the same 

 height on opposite sides of the valley. 



During the summer of 1903 and in con- 

 nection with hydrographic work for the 

 U. S. Geological Survey I had the oppor- 

 tiinity to examine most of the streams on 

 Long Island with respect to the visible 

 effects of deflection, and although many of 

 the valleys on the south side of the island 

 have a noticeably unsymmetrical develop- 

 ment, one bank being steeper than the other, 

 an actual count of the valleys from Mon- 

 tauk Point to Par Rockaway shows such a 

 small majority of valleys asymmetrically 

 developed and with the right bank steeper 

 than the left, that in this case the argument 

 based on deflective tendency does not ap- 

 pear well-grounded. The cuesta-like ar- 

 rangement of the slopes on the island and 

 the consequent great disparity of stream 

 lengths, velocity and persistence through- 

 out the year, precludes frviitful comparison 

 of valleys on the northern and southern 

 sides of the island as showing in how far 

 the difference in composition of wind force 

 and deflective tendency affects the fashion- 

 ing of the valley slopes. 



Isaiah Bovfman. 



Ypsilanti, Mich. 



SCIENTIFIC BOOKS. 

 Lehrljuch der Physik; Zweiter Band. Von O. 

 D. Chwolson, St. Petersburg; iibersetzt 

 von H. Pflaum. Braunschweig, Friedrich 

 Vieweg und Sohn. 1904. Pp. 1056. 

 The first volume of the German edition of 



