Alexander von Humboldt Quote

Conclusions based upon analogies may fill up a portion of the vast chasm which separates the certain results of a mathematical natural philosophy from conjectures verging on the extreme, and therefore obscure and barren confines of all scientific development of mind.

Translated by E.C. Otte, Cosmos: A Sketch of a Physical Description of the Universe (Volume 3), Special Results of OBSERVATION IN THE DOMAIN OF COSMICAL, PHENOMENA (p. 29)