[Joseph] Le Conte
Yosemite Sep' 13th 
Prof' Le Conte
Dear sir, I trust that the latter part of your long vacation ramble was as full of scientific & universal joy as the week that I had the happiness of spending with you, Doubtless you are home again, & with your classes, & have answered all the uppermost outside questions of your friends relative to your journey, & I come to you now to beg a letter fa[illegible] or so if observations made after we part- ed. upon whatever you think will most interest me. I reached the highest of those volcanic cones without extraordinary difficulty, & was surprised to find its smooth sloping sides composed of volcanic sand instead of ashes, the inside of the crater was nearly full of the same material, & no marks of recent activity were apparent anywhere. The sand of its sloping sides was mostly or altogether
derived from the solid lava by ordinary disintegration, & extends out on the plain as far as the right bank of Rush Creek. I could not detect the slightest difference between the sand of this volcano & that of which the encompassing ring of the one we visited in company is composed - I found the same kind of glacial boulders in the same abundance, & in similar positions to those we found in the first crater, & the boulders in the higher & apparently older cone were in the same condition as those of the lower one, even those which had been subjected to a degree of heat that caused their glacial polish to flake off, seemed to have suffered no greater change by disintegration. I do not think that any portion of that stratified volcanic rock which we saw on Rush Creek was derived from these volcanoes, but rather that they (the volcanoes) are of a later age & derived the boulders found in their lava from that drift stratum which we discovered on the creek
It is my opinion that the encircling [ground?] of sand of the remarkably low crater which we visited together is the [base deleted] undisturbed base of a cone of about the same age as the higher ones of the range, & was isolated into its ring shape by the subsidence of the cone to which it belonged. The narrowness of the top of the mound, & the acutness of the angle formed by the slope of its inner surface, & the side of the re- maining portion of the cone, would thus be accounted for. Those fresh surfaces of lava blocks do not appear to me as proofs of recent action but only as proofs of recent fracture, because we found masses which were scratched & disintegrated upon one side like the sides of the higher cones, & fresh & unchanged upon the others, & loose sand, & worn blunt angled blocks [were deleted] derived from the outside of the cone before it fell was scattered irregularly throughout the whole extent of the broken crater. Then according to this theory we have not a crater
within a crater, but an ill defined fragmentary crater sunk perpendicularly to a level with its own well defined undisturbed base - Well I will say no more about mono ashes & I assure you that I only send you my opinions to provoke your sending me your own I reached my cabin among the Yosemite ferns on the fourth day after leaving you, & on the journey obtained some new data concerning the depth of the Tuolumne glacier & concerning the numerous rocks of this constant shape I remember the week passed in your com- pany with a great deal of solid earnest pleasure & will be exceedingly happy to accompany you again in rambles to any portion of our glorious star -
I am yours most cordially John Muir
Original letter dimensions: 24.5 x 39 cm.
Muir, John, "Letter from John Muir to [Joseph] Le Conte,  Sep 13." (1870). John Muir Correspondence (PDFs). 1354.
Reel 02, Image 0335
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