74 



SCIENCE. 



[Vol. XI. No. 262 



at twenty-five hundred, it forming tlie bed of the latter stream for 

 twenty miles. 



One of the most interesting portions of the Cascade Range is the 

 region of the Santiam River, in latitude 44° 45' north, — a tributary 

 ■of the Willamette. The lower foot-hills there are composed of a 

 yellowish volcanic ash, stratified in part, and which reaches a thick- 

 ness of several hundred feet. Such deposits are very abundant on 

 the western slope of the range, amply fulfilling Mr. King's acute 

 prediction of their existence (see ' Survey of the 40th Parallel,' vol. 

 i. p. 453). The ash rests upon basalt, which lies in thick layers 

 •conforming to the general westward slope of the range. As we 

 advance into the mountains, the basalt thins out, and at a moderate 

 ■elevation disappears entirely in its general form of surface out- 

 flows, and is seen only as scattered dikes penetrating older rocks. 

 Undoubtedly the basalt rests, as a rule, upon the unaltered sedi- 

 mentary rocks to be referred to in another connection ; but I have 

 ■not observed them at the precise locality of which I speak. At an 

 altitude of perhaps one thousand feet, the later rocks are replaced 

 in the bed of the stream by metamorphic rocks of a slaty texture, 

 which appear to dip westward. Proceeding up stream, and ap- 

 proaching the axis of the range, we find in very deep caiions some 

 ■excellent exposures which illustrate the geological structure in a 

 most remarkable and cogent way. The caiions are clearly of 

 glacial origin, and are cut dowfl three thousand feet or more 

 through rocks of various ages, the lowest ones visible being meta- 

 morphic slates similar in all respects to the auriferous slates of 

 ■California, — a resemblance that is heightened by the fact that the 

 Santiam slates are also auriferous, workable quartz veins existing 

 therein. The slates are nearly vertical, with a slight westerly dip. 

 Upon them rest unconformably a great thickness of clayey and 

 sandy shales, and conglomerates, unaltered, and of course devoid of 

 ■quartz veins, and occupying a nearly horizontal position in general. 

 They are cut by deep caiions into great mountain-masses, and form 

 probably the most important division of rocks at this part of the 

 range. I should judge them to be fully two thousand feet thick, 

 and perhaps three thousand. I have secured no fossils from which 

 their age might be determined, but for statigraphical reasons, with 

 which I will not trouble Science, I shall denote the terrane as creta- 

 ceous until its age be more satisfactorily determined. I am not 

 aware of any description of this formation having ever been pub- 

 lished, nor have I ever heard or read aught concerning it. 



Of later sedimentary rocks, the only existing ones yet discovered 

 are certain fossiliferous sandstones and associated shell limestones, 

 ■which have been spoken of as miocene, and may well belong to 

 that system. They appear in the Cascades as fossil sea-beaches, 

 defining the limits of the miocene ocean. The maximum height 

 at which I have noticed these rocks in the Santiam region is be- 

 tween eight hundred and a thousand feet. 



As might be supposed, the metamorphic slates rest against 

 granite, which here forms the backbone of the range, the upper 

 ■central portions being entirely composed of it and slate, plus a pro- 

 portion of recent lava, which seems to have come from crater erup- 

 tions, but of which I can say little, f desire to call attention to 

 the prevalence of ancient lavas in contradistinction to the more 

 modern basaltic flows. There are heavy bodies of probably au- 

 gitic lava overlaid by and therefore older than the rocks I have de- 

 nominated cretaceous. Other instances seem to prove associated 

 lavas as old as the auriferous slates. Of these eruptive rocks, I 

 recognize two or three general types, which I have forwarded for 

 :study and determination to Professor Jackson, the petrologist at 

 Berkeley, Cal. Altogether, I believe that the eruptives, old and new, 

 make up perhaps one-eighth or one-tenth of the bulk of the visible 

 terranes of the Santiam. 



It is evident that the Santiam section resembles neither the ex- 

 clusively volcanic exposures cited, nor the Umpqua section, as de- 

 scribed by Dr. Becker, who found granite and metamorphic rocks 

 overlaid unconformably by miocene strata, without the presence of 

 intermediate unaltered rocks. Besides, his metamorphic types 

 were chiefly serpentine, which, notwithstanding its immense devel- 

 opment in southern Oregon, I have not noticed north of the Cala- 

 pooia Mountains. It seems not improbable that the serpentines 

 may be the representatives of the unaltered shales and conglom- 

 •erates of the Santiam. 



From the above observations, and from other reasons which I 

 will not take space to explain, I conjecture that the earliest moun- 

 tain-making movement which affected the Cascades took place 

 much farther back than the cretaceous, as held by some, and re- 

 sulted in forcing up the granite nucleus, with its covering of slate 

 or the representatives of slate, to a considerable height above sea- 

 level ; this movement being followed by extensive denudation, 

 of which good evidence appears to exist. Then followed a sub- 

 mergence, total or partial, when the strata that I call cretaceous 

 were laid down. The whole range could hardly have been ingulfed 

 at the time, for I am told of tracts now existing where no interme- 

 diate strata are found between the early granite and the late basalt. 

 I can suggest nothing as to the condition of affairs during the 

 eocene time, the question of the existence of marine strata of that 

 age in Oregon not having received attention. 



It would seem that the miocene strata were deposited on rising 

 areas, when the Cascades had reached to within a few hundred 

 feet of their present height. 



It is probable that there have been at least two upheavals, and one 

 movement of subsidence, which, with attendant phenomena, I have 

 grouped as follows : — 



1. In paleozoic or early mesozoic time, primary elevation of 

 granite axis with overlying sediments, accompanied by metamor- 

 phism of the latter. 



\a. Denudation of range. 



2. Subsidence beneath cretaceous sea, and deposition of creta- 

 ceous strata. 



3. Elevation to within one thousand feet of present state. 

 3 a. Deposition of miocene rocks. 



'},b. Outpouring of lavas through fissures. 



3^:. Era of crater eruptions, and deposition of beds of volcanic 

 tuffs in late seas and lakes. 



3 d. Continued elevation of land to present height, accompanied 

 by glacial and aqueous erosion. Diminished volcanic activity. 



There are certain evidences, among them Captain Dutton's dis- 

 covery of a rising surface at the Cascades of the Columbia, which 

 make it probable that the mountain-making movements are still go- 

 ing on in the range. Herbert Lang. 



Portland, Ore., Jan. 31. 



• Queries. 



27. Washington's Letters. — In the last number of the Mag- 

 azine of American History there are two letters of Washington 

 which I think are of doubtful authenticity. The first letter is 

 printed on p. 162 : the second immediately follows it. Both are 

 claimed to be taken from originals in the collection of Dr. Thomas 

 Addis Emmet. That forgeries are extant of Washington's letters, 

 is well known to collectors. One prominent test of such forgeries 

 is said to be in the autograph. Washington always abbreviated 

 ' George ' by writing ' G°,' and never used the initial G alone. 

 Such a test, if reliable, applied to the letters, would prove them to 

 be forgeries. This test will hold good in comparing the undoubt- 

 edly genuine letters copied from originals in the British Museum, 

 and printed in the same number of the magazine. Again, the sub- 

 ject-matter of these letters is suspicious, especially where Washing- 

 ton is made to write of his troops at Cambridge, that they " are an 

 exceedingly dirty and nasty people." I do not claim to be an ex- 

 pert on such matters. On the contrary, my disbelief in their authen- 

 ticity is based more upon my wish that our beloved Washington 

 did not write such a sentiment. 



George Glenn Wood, M.D. 



Muncy, Penn., Feb. 7. 



Answers. 



23. Drops of Water. — In answer to Mr. E. J. Pond's query 

 in relation to floating drops of water upon the general surface 

 {Science, xi. p. 38), I beg leave to refer him to the paper of Prof. 

 Osborne Reynolds of Manchester (England), published in Nature, 

 vol. XXV. p. 23. Nov. 3, 1 88 1, where he will find an explanation of 

 this capillary-film phenomenon, as well as a clear indication of the 

 physical conditions necessary for its production. 



John LeConte. 



Berkeley, Cal., Jan. 30. 



