August 24-, 1872.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
157 
sent to us from the universe around, we recognize the 
same truth. Thus it is agreed alike by physicists and 
physiologists, that colour does not exist as such in the 
object itself; which has merely the power of reflecting 
or transmitting a certain number of millions of undula¬ 
tions in a second ; and these only produce that affection 
of our consciousnses which we call colour, when they fall 
upon the retina of the living percipient. And if there 
be that defect either in the retina or in the apparatus 
behind it, which we call “colour-blindness” or Dal¬ 
tonism, some particular hues cannot be distinguished, or 
there may even be no power of distinguishing any colour 
whatever. If we were all like Dalton, we should see no 
difference, except in form, between ripe cherries hanging 
•on a tree, and the green leaves around them: if we were 
all affected with the severest form of colour-blindness, 
the fair face of nature would be seen by us as in the 
chiaroscuro of an engraving of one of Turner’s land¬ 
scapes, not as in the glowing hues of the wondrous 
picture itself. And in regard to our visual conceptions, 
it may be stated with perfect certainty, as the result of 
very numerous observations made upon persons who 
Rave acquired sight for the first time, that these do not 
serve for the recognition even of those objects with which 
the individual had become most familiar through the 
touch, until the two sets of sense-perceptions have been 
co-ordinated by experience.* 
When once this co-ordination has been effected, how¬ 
ever, the composite perception of form which we derive 
from the visual sense alone is so complete, that we seldom 
require to fall back upon the touch for any further infor¬ 
mation respecting that quality of the object. So, again, 
while it is from the co-ordination of the two dissimilar 
pictures formed by any solid or projecting object upon 
•our two retinae, that (as Sir Charles Wheatstone’s ad¬ 
mirable investigations have shown) we ordinarily derive 
through the sight alone a correct notion of its solid form, 
there is adequate evidence that this notion, also, is a 
mental judgment based on the experience we have acquired 
in early infancy by the consentaneous exercise of the 
visual and tactile senses. 
Take, again, the case of those wonderful instruments 
by w T hich our visual range is extended almost into the 
infinity of space, or into the infinity of minute¬ 
ness. It is the mental not the bodily eye, that 
takes cognizance of what the telescope and the mi¬ 
croscope reveal to us. For we should have no well- 
grounded confidence in their revelations as to the un¬ 
known, if we had not first acquired experience in dis¬ 
tinguishing the true from the false by applying them to 
known objects ; and every interpretation of what we see 
through their instrumentality is a mental judgment as to 
the probable form, size, and movement of bodies removed 
by either their distance or their minuteness from being 
■cognosced by our sense of touch. 
The case is still stronger in regard to that last addition 
to our scientific armamentum, which promises to be not 
inferior in value either to the telescope or the micro¬ 
scope ; for it may be truly said of the spectroscope, that 
it has not merely extended the range of our vision, but 
has almost given us a new sense, by enabling us to re¬ 
cognize distinctive properties in the chemical elements 
which were previously quite unknown. And who shall 
now say that w r e know all that is to be known as to any 
form of matter; or that the science of the fourth quarter 
•of this century may not furnish us with as great an en- 
* Thus, in a recently recorded case in which sight was im¬ 
parted by operation to a young woman who had been blind 
from her birth, but who had nevertheless learned to work 
well with her needle, when the pair of scissors she had been 
accustomed to use was placed before her, though she de¬ 
scribed their shape, colour, and glistening metallic character, 
she was utterly unable to recognize them as scissors until 
she put her finger on them, when she at once named them, 
laughing at her own stupidity (as she called it) in not 
Luring made them out before. 
largeinent of our knowledge of its properties, and of our 
power of recognizing them, as that of its third has done ? 
But, it may be said, is not this view of the material 
universe open to the imputation that it is “ evolved out 
of the depths of our own consciousness”—a projection of 
our own intellect into what surrounds us—an ideal rather 
than a real world ? If all we know of matter be an “ in¬ 
tellectual conception,” how are we to distinguish this 
from such as we form in our dreams F—for these, as our 
laureate no less happily than philosophically expresses 
it, are “true while they last.” Here our “common 
sense ” comes to the rescue. We“ awake, and behold it 
was a dream.” Every healthy mind is conscious of the 
difference between his waking and his dreaming expe¬ 
riences ; or, if he is now and then puzzled to answer the 
question, ‘^Did this really happen, or did I dream it F 
the perplexity arises from the consciousness that it might 
have happened. And every healthy mind, finding its 
own experiences of its waking state not only self-con¬ 
sistent, but consistent with the experiences of others, 
accepts them as the basis of his beliefs, in preference to 
even the most vivid recollections of liis dreams. 
The lunatic pauper who regards himself as a king, the 
asylum in which he is confined as a palace ot regal 
splendour, and his keepers as obsequious attendants, is 
so “possessed” by the conception framed by his dis¬ 
ordered intellect, that he docs project it out oi himself 
into his surroundings; his refusal to admit the collec¬ 
tive teaching of common sense being the very essence of 
his malady. ° And there are not a few persons abroad in 
the world, wdio equally resist the teachings ol educated 
common sense, whenever they run counter to their own 
preconceptions ; and who may be regarded as in so far 
_affected with what I once heard Mr. Carlyle pithily 
characterize as a “ diluted insanity. 
It has been asserted over and over again, of late years, 
by a class of men who claim to be the only true inter¬ 
preters of nature, that we know nothing but matter and 
the laws of matter, and that force is a mere fiction of the 
imagination. May it not be affirmed, on the othei 
hand, that wRile our notion of matter is a conception of 
the intellect, force is that of which we have the most 
direct—perhaps even the only direct cognizance. As 
I have already showm you, the knowledge of resistance 
and of weight which we gain through oui tactile sense is 
derived from our own perception of exertion-, and in 
vision, as in hearing, it is the force with which the un¬ 
dulations strike the sensitive surface that affects our 
consciousness with sights or sounds. I rue it is that m 
our visual and auditory sensations we do not, as in our 
tactile, directly cognosce the force which produces them; 
but the physicist has no difficulty in making sensible to 
us indirectly the undulations, by which sound is propa¬ 
gated, and in proving to our intellect that the force con¬ 
cerned in the transmission of light is really enormous.* 
It seems strange that those wRo make the loudest ap¬ 
peal to experience as the basis of all knowledge, should 
thus disregard the most constant, the most fundamental, 
the most direct of all experiences ; as to which the com¬ 
mon sense of mankind affords a guiding light much 
clearer than any that can be seen through the dust of 
philosophical discussion. For, as Sir John Herschel most 
truly remarked, the universal consciousness of mankind 
is as much in accord in regard to the existence of a real 
and intimate connection between cause and effect, as it 
is in regard to the existence of an external world; and 
that consciousness arises to every.one out of his own 
sense of personal exertion in the origination ot changes 
by his individual agency. . . , p ... f 
Now while fully accepting the logical definition of 
cause as the “ antecedent or concurrence of antecedents 
m which the effect is invariably and unconditionally 
consequent,” we can always single out one dynamical an- 
* See SR John Herschel’a ‘ Familiar Lectures on Scientific 
Subjects.’ 
