Alexander G. McAdie


John Muir


image preview


2think the clouds resembles humans. They are just as restless, seem never quite at ease and often surge hither and thither like an excited populace. Again, some rise steadily and some fall. Some are joys forever to the eyes below, beholding them; some are but confused and uncertain wanderers; and some, when most is expected of them, fade away, casting only a shadow, when a thirsty land hoped for rain.The water vapor condenses,it is thought, only when minute nucleis are present to serve as centers of condensation. It is claimed that in a perfectly dust-free air no drops will form; but light may ionize air that we would otherwise consider dust-proof, and the necessary nuclei [Illegible] present. Out in the open probably there is never a time that cloud particles could not form provided the supply of water-vapor is present. The average size of a rain drop is from two to four millimeters. The largest drops are about seven mm. Fine drops fall at varying rates and drops take on various sizes with facility. With very fine drops the viscous resistance of the air prevents falling. Professor Lenard of Kiel, about five years ago, published a paper on his experiments with rain drops. He produced vertical currents of air which could be regulated and measured, and drops of various sizes falling04734


San Francisco

Date Original

1910 Mar 19


Original letter dimensions: 25 x 20 cm.

Resource Identifier


File Identifier

Reel 19, Image 0257

Copyright Statement

Some letters written to John Muir may be protected by the U.S. Copyright Law (Title 17, U.S.C.). Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Responsibility for any use rests exclusively with the user.

Owning Institution

University of the Pacific Library Holt-Atherton Special Collections. Please contact this institution directly to obtain copies of the images or permission to publish or use them beyond educational purposes.

Page Number

Page 2


John Muir, correspondence, letters, author, writing, naturalist, California, correspondent, mail, message, post, exchange of letters, missive, notes, epistle