February lo, 1888.] 



SCIENCE 



75 



in accordance with the reflex innervation, if we may call it such, 

 for adjustment. But we shall not enter upon this in our present 

 problem. We have mainly to notice that a and c will not fuse 

 while the latter, c, can fuse with b. Now, as no greater degree of 

 convergence is required for the combination of b and c than for A 

 and B, their combined image will appear in the same plane as that 

 of A and B. This is of course relatively a monocular localization. 

 But, singularly enough, there is a binocular effort, as it were, in 

 one eye, to combine a with c ; and the result is that a appears 

 nearer the observer than the combined image of A and B, without 

 in the least translocating the fused image of b and c from their 

 position in the plane of A and B, and without separating them to 

 produce any fusion of a and c, although the latter can be effected 

 if we will. Rivalry will at times suppress the translocated image 

 of a, so that it appears monocularly located in the same plane with 

 b and c, or A and B. The alternations may be very distinctly ob- 

 served. But here we have a very evident case of binocular inner- 

 vation in one eye, and localization of a in accordance with it 

 nearer the observer ; while no such binocular translocation and in- 

 nervation take place for the fused image of b and c, because it 

 preserves a constant relation to that of A and B. b and c sustain 

 the same relations of distance to the median plane, and hence will 

 be monocularly localized in the same position of the third dimen- 

 sion as A and B, although binocularly combined. Whatever of 

 tension or innervation there may be in the left eye for binocular 

 combination of c with a is counteracted by the opposite tension to 

 retain the fusion of b and c, which remaijis located in the plane of 

 A and B, or, better, of their fused image. Thus there is left only 

 the binocular innervation of the right eye to translocate the image 

 of a to a position nearer the observer than the other images, except 

 when this tension is suppressed by rivalry. Then a .is located at 

 the same distance as the others. • The incident is interesting as 

 showing that there may be rivalry between binocular and monocular 

 functions for localization in the third dimension as well as the 

 ordinary rivalry between colors in plane dimension. It confirms 

 also the results of the first experiment we have described. 



We have presented these phenomena to suggest the possibility 

 that monocular influences, apparent in the instances noted, may 

 account for many irregularities and illusions in binocular vision 

 as practised by the experimenter to investigate localization. Why 

 may not rivalry between them suppress certain impressions, so that 

 the effect may appear to be different from what it really is ? Why 

 may it not account for the failure of stereoscopic combination of 

 two real objects to translocate their fused image to the point of 

 fixation .' We do not insist that our explanation must be correct : 

 nor will too great stress be laid upon our conjectures without some 

 verification from the experience of others. To our experience there 

 seems no other way of looking at the matter. 



J. H. Hyslop. 



Baltimore,Md., Jan. 31. 



Transcontinental Railroads. 



In treating the subject of transcontinental railways. Science (x. 

 No. 241) uses language to the effect that the Cascade Range of 

 Oregon and Washington is known to be a continuation of the Sierra 

 Nevada, and mentioning as a striking and all-important structural 

 difference that the Cascades are volcanic, while the Sierra is gra- 

 nitic, therein assuming as facts two propositions which have been 

 much debated, but which, in the present state of geological knowl- 

 edge, can hardly be demonstrated. In order to learn the progress 

 of opinion respecting the connection of the two ranges, readers of 

 Science should consult the American Journal of Sciences, third 

 series, vol. vii. p. 177, wherein Prof. Joseph LeConte suggests the 

 idea, original with himself I believe, of the unity of the two ranges 

 in age and cause. 



Second, Clarence King, in ' Geology of the 40th Parallel,' pp. 

 441-454, extending theory far beyond the support of adequate ob- 

 servation, held that the Cascades were separated in age from the 

 older Sierra by a vast time-interval (to wit, the whole of the cre- 

 taceous period), and that the Blue Mountains of eastern Oregon 

 were the real continuation of the Sierra. 



Third, Dr. Becker of the United States Geological Survey, basing 

 his opinion on the finding of granitic and metamorphic rocks in the 



caiion of the Umpqua River in the southern Cascades, remarks (see 

 Bulletin 19, United States Geological Survey) that that portion of 

 the range has a foundation similar to the California ranges, and is 

 probably due to the same upheaval. He thus maintains a proper 

 reserve as to the general question. 



Lastly, Mr. Diller (Bulletin 33, United States Geological Survey),, 

 after examining the stratigraphical relations of the Cascades, Sierra,, 

 and Coast Range at their presumed point of divergence in northern 

 California, while quoting Dr. Becker's discovery and opinion, sums 

 up his own conclusions thus : " As far as is definitely known, the 

 Cascade Range was not represented by a ridge of older metamor- 

 phic rocks which were folded and upheaved at the same time with 

 the Sierra and the older portion of the Coast Range, and is entirely- 

 distinct from them in strtictiir'e and origin." In another connec- 

 tion he says, " Such rocks [granitic and metamorphic] make up the 

 Coast Range west of Mount Shasta, and it may be that they form 

 an elevated foundation for the Cascades between Rogue River and 

 Mount Hood ; but this is rendered less probable by the complete 

 section along the Columbia River, where the range is cut across 

 nearly to sea-level, showing, according to Professor LeConte, that 

 it is made up almost wholly of recent lavas resting on undisturbed 

 miocene strata." Mr. Diller, of his own observation, announces 

 that the Cascades, where intersected by the Klamath River, are 

 also composed exclusively of recent eruptive rocks. Thus the mat- 

 ter stands to-day, and it is doubtful if the question of a simultaneous 

 origin is to be settled on other than paleontological grounds, by a 

 careful and minute comparison of fossil evidences. 



The second assumption, that the two ranges differ in the one 

 being granitic, the other volcanic, I dare say, is but the reflection of 

 the common belief which took its rise from the circumstance of the 

 only known or visited section, that ot the Columbia gorge, being 

 entirely volcanic, but is nevertheless a most indiscriminating and 

 erroneous opinion, as I will endeavor to show. 



I find that the drift brought down by the ancient glaciers of the 

 Cascades, and deposited in the valleys below, invariably contains 

 a proportion, though very variable, of granitic and sedimentary 

 bowlders. In some cases, particularly of certain ice-streams which 

 flowed into the Willamette valley (which, by the way, is covered for 

 the most part with glacial debris to a great depth), the granite and 

 metamorphic bowlders and gravel predominate immensely ; some- 

 times, indeed, to the exclusion of volcanic sorts. The prevailing 

 types in most other drift localities, however, are volcanic. The 

 significance is that a part of the rock-masses eroded by the ancient 

 glaciers were granitic and metamorphic beyond a doubt ; and, in 

 the cases where transported bowlders prevail, the parent granitic 

 and metamorphic rock-masses from which they were derived must 

 have preponderated over the volcanic masses. I leave the question 

 of the comparative erodibility of the various rock-masses, as well 

 as the considerations arising from their relative positions, all of 

 which must have had influence on the proportions of granitic, meta- 

 morphic, and volcanic glaciated bowlders. 



But we need not depend upon the accidental evidences of extinct 

 glacial action to prove the composition of the Cascades, for 

 examinations of the range at different points have shown me 

 that it is not exclusively volcanic by any means ; indeed, I doubt 

 much if the granitic and metamorphic rocks do not preponderate 

 over the volcanic rocks, viewing the range as a whole. Judging by 

 the evidence of formations in situ, I should say, notwithstanding 

 the existence of exclusively volcanic sections, that the foundation 

 of the range in general is not unlike that of the Sierra, excepting 

 that I see no indication of the great orographic blocks which, ac- 

 cording to Mr. Diller, compose the northern Sierra. 



Judging from what has been published concerning the range, the 

 prevailing idea of its structure seems to regard it as composed of a 

 single anticlinal ridge composed wholly of basalt, and crowned 

 with snow-covered conical peaks set at regular distances along the 

 range. Geologists who have this idea will be surprised to learn 

 that granite appears in the range at an altitude of two thousand 

 feet, within eight miles of the Columbia. This is on the north side 

 of the river ; while on the south, towards Mount Hood, it is said to 

 be found at five thousand feet. I cite only the former instance as 

 observed by myself. I also find granite on the Santiam River at a 

 height of five thousand feet above sea-level, and on the McKenzie 



