July 26, 1895.] 



SCIENCE. 



99 



cation of an originally irregular shore line 

 by cutting o& headlands and throwing bars 

 across bays. 



In other States, the Bath (Maine) sheet 

 is a remarkably eidfective illustration of a 

 ragged coast line ; it includes the north- 

 ward deflection — presumablj^ by drift bar- 

 riers — of the Androscoggin at Brunswick 

 to the expansion of the Kennebec in Merry- 

 meeting bay. Wood River, Grand Island, 

 Minden and Kearny sheets, Nebraska, show 

 how the overburdened Platte sprawls across 

 the Plains in its many channels. The shore 

 line on the Seattle (Wash.) sheet has a 

 number of low cuspate points, apparently 

 small-scale examples of the action of eddy- 

 ing currents. For the most of us who can- 

 not see the country itself, these maps are 

 highly illuminating and suggestive. 



THE DELAWARE AVATER GAP. 



The plunging Medina sandstones that 

 form Kittatinny mountain, the wall on the 

 northern side of the Great Appalacian val- 

 ley in Pennsylvania, are trenched across by 

 a number of streams, all flowing from the 

 region of the inner Alleghany ridges south- 

 east towards the sea. It may be plausibly 

 suggested that the ancestors of these streams 

 originally ran to the northwest, as the ISTew- 

 Kanawha of Virginia still does ; but that 

 in Pennsylvania the drainage was after- 

 wards turned to the present direction of 

 discharge in some manner not now well 

 defined but probably dependent on moderate 

 deformation and the associated shifting of 

 divides. The date of this change is not 

 settled, but it is supposed to have been be- 

 fore the post-Cretaceoiis elevation of the 

 region. This would imply that the Ter- 

 tiary excavation of the broad longitudinal 

 and the narrow transverse valleys or water 

 gaps was accomplished by rivers running 

 as a whole in their present courses. 



A recent article by Emma Walters (Does 

 the Delaware water gap consist of two 



river gorges? Proc. Acad. Nat. Sci., Phila., 

 March, 1895) takes another view in sug- 

 gesting that the most noted of the water 

 gaps is the work of a river that ran north- 

 ward for most of the time while it was cut- 

 ting down the gap, and that it assumed its 

 present direction in comparatively recent 

 time. The local and immediate evidence 

 quoted to indicate a northward flow is a 

 pool, fifty to seventy feet deep, on the north- 

 ern side of the hard sandstone sill of the 

 gap ; but the excavation of such a pool 

 seems to be within the power of a strong- 

 river flowing in a narrow, curved channel. 

 Collateral evidence of northward flow is 

 found in the favorable interpretation of a 

 number of indecisive observations made by 

 various geologists, but the value of this 

 kind of evidence is very uncertain. 



W. M. Davis. 

 Haevaed XJniveksity. 



PSYCHOLOGICAL NOTES. 

 THE SENSE OF EQUILIBRIUM. 



Dr. a. Crum Brown, in a lecture on ' The 

 Relation between the Movements of the 

 Eyes and the Movements of the Head' 

 (printed in The Lancet, May 25th, and in 

 Nature, June 20th), reviews the evidence 

 that has led to the assumption that the 

 semi-circular canals (together with the 

 utricle and sacule) of the inner ear are 

 sense-organs, giving us our information 

 concerning position and equilibrium of the 

 body. This view is now universally ac- 

 cepted, although the evidence is only cir- 

 cumstantial and not altogether conclusive 

 to the present writer. There is no doubt 

 but that injuries to the semi-circular canals 

 cause corresponding disturbances in equi- 

 librium, but dizziness and sickness are also 

 caused by visual sensations. We may be- 

 come dizzy from watching a waterfall, and 

 when whirled about grow dizzy much more 

 quickly when the eyes are open than when 

 they are closed. It would seem that 



