SCIENCE. 



453 



event, with all its attendant circumstances, appeared so 

 familiar to him that he was absolutely sure he had pre- 

 viously experienced the same impressions, surrounded by 

 the same people or objects, with the same sky, weather, 

 etc. If he ventured to undertake a new occupation of 

 any kind whatever, he was certain he had done it before 

 and under identical conditions. Sometimes the sen- 

 sation would occur the same day, in the course of a few 

 minutes or hours, sometimes it did not strike him until 

 the day following, but it was always a distinct impression. 



In this phenomenon of false memory, there is an 

 anomaly of mental mechanism which escapes us, and 

 which is difficult to comprehend in a healthy state. The 

 person affected, no matter how acute an observer he 

 might be, could only analyze the condition when he 

 ceased to be deceived by it. From the examples given it 

 would seem to me that the impression received is repro- 

 duced in the form of some image. To employ a physio- 

 logical term, there is a repetition of the primative cerebral 

 process. This is a very ordinary phenomenon. It occurs 

 in every recollection which is not caused by the actual 

 presence of the object. The only difficulty is to discover 

 why this image which arises a minute, an hour or a day 

 after the real condition, should appear to be a repetition 

 of the latter. We may possibly admit that the mechan- 

 ism of recollection acts in a distorted manner, for my 

 part, however, the following explanation seems more ex- 

 plicit : 



The image formed in this manner is very intense and 

 partakes of the nature of an hallucination. It is, appar- 

 ently, a reality, for nothing rectifies the illusion. Conse- 

 quently, the real impression is forced back, as it were, and 

 assumes the character of a recollection. It becomes 

 realized in the past, erroneously if we consider the facts, 

 objectively, properly, if we consider them subjectively. 

 The hallucination, although very vivid, does not efface 

 the actual impression, but as the latter is quite separate, 

 and as the former is produced at a comparatively late 

 period, the real occurrence appears to be a second ex- 

 perience. The hallucination assumes the place of the 

 actual impression, it seems to be more recent, and this is 

 really the case. Of course, to us who judge according 

 to what we see externally, it is false to say that the im- 

 pression was received twice. To the person afflicted, 

 however, who determines solely as his consciousness 

 may dictate, it is true that the impression was actually 

 received twice. 



To the support of this explanation, I would call atten- 

 tion to the tact that false memory is nearly always allied 

 to si^me mental affection. The person mentioned by 

 Pick suffered from a form of insanity. He was contin- 

 ually endeavoring to escape from people he supposed 

 were his persecutors. Hallucinations in this instance 

 would be perfectly natural. I do not, however, wish to 

 assert that my theory is the only possible one. In regard 

 to this isolated condition of false memory, much more 

 numerous and concise observations than mine are prob- 

 ably required. 



THE EXCAVATION OF THE GRAND CANON 



OF THE COLORADO RIVER.* 



By Capt. C. E. Dutton, U. S. A. U. S. Geological Survey. 



The Grand Canon of the Colorado River is the 

 longest, widest and deepest of the almost continuous 

 chain of canon valleys through which the upper half of 

 that river flows. Its length is 218 miles, its width from 

 5 to 1 1 miles, and its depth from 4500 to 6000 feet. For 

 convenience of discussion it may be arbitrarily divided 

 into four divisions : 1st. The Kaibab division ; 2d. The 

 Kanab ; 3d. The Uinkaret : 4th. The Sheavwits division. 

 The upper or Kaibab division is the grandest, widest 

 and most diversified, and a little deeper than the others 



* Read before the A. A. A. S. Cincinnati, 1881. 



The three others are simpler in form and much alike in 

 their topographical features. Capt. Dutton first exhibi- 

 ted a view of the canon in the Uinkaret division, showing 

 its simplest and most typical form. It consists of an 

 inner and an outer chasm, or a canon within a canon. 

 The outer chasm is five to six miles wide, and is walled 

 on either side with palisades 2000 feet high, of singularly 

 noble and graceful profiles, which confront each other 

 across a comparatively smooth plain. Within this plain 

 is sunken the inner gorge, descending 3000 feet lower, 

 and having a width a little greater than its depth. At 

 the bottom of the inner gorge flows the Colorado River, 

 a stream about as large as the Ohio between Pittsburg 

 and Wheeling. The strata in which the chasm is cut 

 are chiefly of carboniferous age. The summit of the 

 outer canon wall is very near the summit of that series. 

 The chasm throughout the greater part of its extent 

 cuts below the carboniferous and penetrates the Lower 

 Silurian, and even the Archasan schists, revealing the 

 fact that before the carboniferous was deposited the 

 country had been extensively ravaged by an erosion 

 which swept away heavy bodies of Silurian, and probably 

 also of Devonian strata. The carboniferous now rests 

 upon the beveled edges of the flexed older strata, and 

 in many places rests upon the completely denuded 

 Archaean. 



The region adjoining the chasm and for 40 to 60 miles 

 on either side is a nearly level platform presenting the 

 summit beds of the carboniferous system patched over 

 here and there with fading remnants of the Permian. The 

 strata is very nearly, but not quite horizontal. There is a 

 slight dip to the northward rarely exceeding one degree, 

 but as the general course of the river is along the strike, 

 the edges of the strata disclosed in the Canon walls are to 

 all appearances rigorously horizontal. 



From 40 to 60 miles north of the river are found the 

 principal masses of the later formations, including the 

 Permian, Trias, Jurassic, Cretaceous and Lower Eocene. 

 These form a series of terraces rising successively like the 

 steps of a gigantic stairway as we move northward. Each 

 formation is terminated southwardly by a great cliff and 

 the strata are nearly horizontal, collectively they have been 

 named the Southern Terraces of the High Plateaus. The 

 latest formation which was deposited in this region was 

 the Lower Eocene. 



To the geologist it is obvious that the formations of the 

 Terraces now terminated by gigantic cliffs once extended 

 further out towards the southward and formerly covered 

 regions from which they have been denuded. Captain 

 Dutton is confident that all these terrace formations once 

 reached entirely across the Grand Canon platform in 

 full volume, and that their ancient shore line is found in 

 Central Arizona. The thickness of the strata thus de- 

 nuded was a little more than 10,000 feet on an average, 

 and the area from which they have been swept away is 

 more than 13,000 square miles. It is through the heart 

 of this denuded region that the course of the Grand Can- 

 on is laid. The denudation began probably at an epoch 

 not far from Middle Eocene time, since at that epoch took 

 place the final emergence of the region from a marine con- 

 dition (through the brackish water and lacustrine stages) 

 to the condition of terra firma. 



It is apparent that the cutting and development of the 

 present Grand Canon is only a closing episode of a long 

 history of erosion, extending from Middle Eocene time 

 down to the present. Before the river could begin its 

 attack upon the summit beds ol the carboniferous which 

 now form the crests of its upper walls, it had to cut 

 through more than 10,000 feet of superior strata. This 

 would alone indicate that the beginning of the present 

 canon cannot date far back in Tertiary time, and Capt. 

 Dutton thinks that the evidence points strongly to the 

 conclusion that its excavation in the carboniferous began 

 in Pliocene time. This evidence is cumulative and not 

 1 direct, but is derived from a comparison of many groups 



