USE OF THE IMA GIN A TION. 419 
to take you beyond the boundary of mere observation, 
into a region where things are intellectually discerned, 
and to show you there the hidden mechanism of optical 
action. 
But how are those hidden things to be revealed? Philos- 
ophers may be right in affirming that we cannot transcend 
experience: we can, at all events, carry it a long way from 
its origin. We can magnify, diminish, qualify, and com- 
bine experiences, so as to render them fit for purposes 
entirely new. In explaining sensible phenomena, we 
habitually form mental images of the ultra-sensible. There 
are Tories even in science who regard Imagination as a 
faculty to be feared and avoided rather than employed. 
They have observed its action in weak vessels, and are un- 
duly impressed by its disasters. But they might with 
equal justice point to exploded boilers as an argument 
against the use of steam. With accurate experiment and 
observation to work upon, Imagination becomes the archi- 
tect of physical theory. Newton's passage from a falling 
apple to a falling moon was an act of the prepared imagi- 
nation, without which the " laws of Kepler" could never 
have been traced to their foundations. Out of the facts of 
chemistry the constructive imagination of Dal ton formed 
the atomic theory. Davy was richly endowed with the 
imaginative faculty, while with Faraday its exercise was 
incessant, preceding, accompanying and guiding all his 
experiments. His strength. and fertility as a discoverer is 
to be referred in great part to the stimulus of his imagina- 
tion. Scientific men fight shy of the word because of its- 
ultra-scientific connotations; but the fact is that without 
the exercise of this power, our knowledge of nature would 
be a mere tabulation of co-existences and sequences. We 
should still believe in the succession of day and night, of 
summer and winter; but the conception of Force would 
vanish from our universe; causal relations would disappear, 
and with them that science which is now binding the parts 
of nature to an organic whole. 
I should like to illustrate by a few simple instances the 
use that scientific men have already made of this power of 
imagination, and to indicate afterward some of the further 
uses that they are likely to make of it. Let us begin with 
the rudimentary experiences. Observe the falling of heavy 
rain-drops into a tranquil pond. Each drop as it strikes 
