men and animals on the surface become absolutely invisible
 Jules Verne, Five Weeks in a Balloon (1863). copy citation

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Author Jules Verne
Source Five Weeks in a Balloon
Topic invisible animal
Date 1863
Language English
Reference
Note Translated by William Lackland
Weblink https://en.wikisource.org/wiki/Five_Weeks_in_a_Balloon

Context

“At the height of six thousand feet, the density of the atmosphere has already greatly diminished; sound is conveyed with difficulty, and the voice is not so easily heard. The view of objects becomes confused; the gaze no longer takes in any but large, quite ill-distinguishable masses; men and animals on the surface become absolutely invisible; the roads and rivers get to look like threads, and the lakes dwindle to ponds. The doctor and his friends felt themselves in a very anomalous condition; an atmospheric current of extreme velocity was bearing them away beyond arid mountains, upon whose summits vast fields of snow surprised the gaze;” source