John Muir


John Muir


[Joseph] Le Conte


[on letterhead: Pen Sentinel Hotel, A. C. BLACK, Proprietor.]
Yo Semite Valley, April 20 1872

Dear Le Conte, Yours of Jan 19th was duly re'cd I am glad to know that you hope to gather your thoughts concerning mountains into definite form & that you will certainly come here & glean facts in this magnificent region. Sometime last fall I sent you a letter made up of facts, hints, & guesses concerning mtn' structure wh you may not have rec'd. At least I have not had any answer to it. Therefore I will repeat a portion wh I hope may interest you


Cross Section of West Slope of Sierras through Merced basin with Slates reconstructed upon the [divided?] granite up to the present level of Summit Slates & those of foot of the ranges

In the grass between A & B where the slates are awanting they are always to be found upon the summits of speirs & peaks of sufficient height as on the Hoffman range & the highest peaks of the Merced group. In many places where slate is absent on comparatively high mtns the quality of the granite proves that the line of separation from the slate is nearly reached. - Damdation hs been greatest just where we would expect it to be viz between A & B for there glaciers would according to present data attain their greatest depth. Lower, they would gradually shallow by increasing warmth of temperature. Higher they would be gradually less accumulated until they curved unswedged up against sharp naked summits or against nearly motionless tablelands of ice Glaciers are removing Slates from the granite now I think that this piece of mtn restoration will please you It was you wh first directed my attention in this direction & I am delighted to find your suggest- ions bearing such glorious fruit. I will not at present guess concerning the depth of slate Strata wh have been removed nor of other strata still higher. but of this I am sure. The present Summits of the range are fragments wh have been cut down this (Section 2) from a height wh I will not regard at this time. Also, the present axis of the main range does not

[on letterhead: Pen Sentinel Hotel, A. C. BLACK, Proprietor.]

Yo Semite Valley ______________187

coincide with the present line of summits but lies to the East ward of them, because the range runs to the West of North & consequently the West side of the range received more heat & the west side glaciers were more wasted in summer & kept smaller than those of the more sheltered eastside, & were not able to do so much denudation work, therefore the main axis was overridden after being sharpened to a crest, & the summits gradually pushed westward to their present positions Section 2


Geological axis

CAD present outline of D The crest of every main cross section of summits & spur summit out of sun balance has been pushed thus to the warmer side

A B Line of successive glacier-made summits gradually driven from axis westward

[in margin: Besides these at 33° E lines there are others which we will see & study hereafter. I have a thought or two & some facts [illegible] glacial flora of this region [illegible] you call attention, come for writing is discouraging with such truths. Cordially yrs John Muir By summits I mean any mountain [wave?] sufficiently high for glacier fountains.]

Direction of vertical lines of cleavage at 34 points of observation scattered over the dome-plum[illegible] section below

North 35° E " 35 " Look upon Whitneys map & observe how all " 35 " East & West divides of glacier controlling height have " 35 " been bent Southward. I hope to see you " 30 " soon & will therefore wait my Mary says " 30 " etc. " 30 " " 30 " " 35 " " 35 " " 35 " [drawing] " 40 " " 35 " " 65 " " 45 " " 40 " " 45 " " 25 " " 25 " " 35 " Horizontal Section of Sierras Structure of granite with reference to " 35 " North 33° East lines of cleavage? --------- " 35 " This portion of the Sierra is made up of granite Slates " 20 " S N on edge in a nearly perpendicular position & with " 45 " horizontal direction of North 33.25° East " 35 " These cleavage lines must be of great significance " 30 " because of their universality & age. They swerve not " 30 " for any Dome or canon. Some are of clearer development " 30 " then others & in crossing [narrow Dome & brow forms of rock?] ( 5 W) & various canons these cleavage lines of supposed development yield grand " 20 " testimony concerning glacier " 25 " sculpture. I have never seen a dome so hard as to jostle " 35 " these cleavage seams, however homogeneous in appearance " 35 " all granite of this region in canon bottoms or on summits either " 35 " show or may be made to show these lines. Only a few seams are developed so as to be readily traceable for miles, but spray of a fall will develop them to any degree of dest[illegible] or abundance So I say that these mtns are made of slabs of indefinite thinness set on edge at right angles to the direction of the range.

[in margin: a block of mtn granite as sec 4 when sprayed by a fall developes to Sec 5 with regular & [measurable?] seams]


Yosemite Valley

Date Original

1872 Apr 20


Original letter dimensions unknown.

Resource Identifier


File Identifier

Reel 02, Image 0773

Collection Identifier

Online finding aid for the microform version of the John Muir Correspondence

Copyright Statement

The unpublished works of John Muir are copyrighted by the Muir-Hanna Trust. To purchase copies of images and/or obtain permission to publish or exhibit them, see

Owning Institution

The Bancroft Library, University of California at Berkeley. Please contact this institution directly to obtain copies of the images or permission to publish or use them beyond educational purposes.

Copyright Holder

Muir-Hanna Trust

Copyright Date



4 pages


Environmentalist, naturalist, travel, conservation, national parks, John Muir, Yosemite, California, history, correspondence, letters



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.