John Muir


[John Muir]


[Osgood & Smith]


[Original in possession of Sarah Muir Galloway] [Indianapolis, winter of 1866-67]. Gentlemen: [Osgood & Smith?] The belt system of your shop is in a bad condition, and as belting is at once the nerves and sinews of factory life, the greatness of the importance of having it kept in good order need scarce be urged. The difficulties seem to be: 1st Many belts are not right with regard to tightness 2nd " " have bad joinings 3rd " " are carelessly subjected to friction and thus torn and worn. I carried home a piece of belting to study the effects of atmospheric changes upon it by means of the instrument herein sketched, and the result of my observations as far as they bear practically upon the matter in hand is simply that leather is expanded definitely and considerably by ordinary variations of temperature. Belts, then, are longer in the day when running than during the night, not only because night is colder than day. but because they are heated more or less by friction on the pulley. Therefore if a belt be sufficiently tight when running it should be off the pulley at night. Otherwise it is liable to be strained and its elasticity destroyed by contraction, and when afterwards warmed by running it will be too loose and work imperfectly or portions of the belt must be repeatedly removed. [diagram] A is a strip of leather belting attached to the frame at B, the other end attached to a cord which passes over the pulley P upon the hand [ ] a single glance at the instrument will show that any contractions and expansions that may occur in the belt will be indicated upon the graduated arc.


[Indianapolis, Ind.]

Circa Date

[1866-67 Winter]


Original letter dimensions: 33.0 x 21.5 cm

Resource Identifier


File Identifier

Reel 01, Image 0972

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The unpublished works of John Muir are copyrighted by the Muir-Hanna Trust.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, click here to view the Holt-Atherton Special Collections policies.

Owning Institution

Holt-Atherton Special Collections, University of the Pacific Library. 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



1 page


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



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