3IO 



NA TURE 



\Auo. 15, 1872 



be that defect either in the retina or in the apparatus behind it, 

 which we call " colour-blindness" or Daltonism, some particular 

 hues cannot be distinguished, or there may even be no power of 

 distinguishing any colour whatever. If we were all like Dallon, 

 we should see no dilTerence, except in form, between ripe 

 cherries hanging on a tiee, and the green leaves around them ; if 

 we were all affected with the severest form of colour-blindness, 

 the fair face of Nature would he seen by us as in the chiaroscuro 

 of an Kngraving of one of Turner's Landscapes, not as in the 

 glowing hues of the wondrous Picture it.'elf. 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 

 have 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, however, 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 information respecting the quality 

 of the object. So again, while it is from the co-ordination of 

 the two dissimilar pictures formed by any s^lid or projecting ob- 

 ject upon our two retina;, that (as Sir Charles Wheatstone's 

 admirable investigations have shown) we ordinarily derive through 

 the .Sight alone a correct notion of its solid form, there is ade- 

 quate evidence that this notion, also, is a m^vtitA judgment based 

 on the experience we have acquired in early inlancy by the con- 

 sentaneous exercise of the Visual and Tactile senses. 



Take, again, the case of those wonderful insiruments by which 

 our Visual range is extended almost into the infinity of Space, or 

 into the infinity of Minuteness. It is the mental not the bodily 

 eye, that takes cognizance of what the Telescope and Microscope 

 reveal to us. For we should have no well-grounded confidence 

 in their revelations as to the unknown, if we had not first acquired 

 experience in distinguishing the true from the false by applying 

 them to known objects ; and every inierpretation of what we see 

 through their instrumentality is a mental judgment as to the pro- 

 bable form, size, and movement of bodies removed by either 

 their distance or their minuteness froin being cognosced by our 

 sense of Touch. 



The case is still stronger in regard to that last addition to our 

 Scientific aimatnenium, which promises to be not inferior in 

 value either to the Telescope or the Microscope ; 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 recognise distinctive properties in the Chemical 

 Elements which were previously quite unknown. And who shall 

 now say that we know all that is to be known as to any form of 

 Matter ; or that the science of \\\e. fourth quarter of this century 

 may not furnish us with as great an enlargement of our know- 

 ledge of its Properties, and of our power of recognising them, as 

 that of its third \\3!, 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 " Intellectual Conception," how are weto 

 distinguish this from such as we form in our Dreams ? — for these, 

 as our Laureate no less happily than philosophically expresses it, 

 are "tnie 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 experiences ; or, if he is now and then puzzled 

 to answer the question, " Did this really happen, or did I dream 

 it?" the perplexity arises from the consciousness that it might 

 have happened. And every healthy mind, finding its own ex- 

 periences of its waking slate not only self-consistent, but con- 

 sistent with the experiences of others, accepts them as the basis of 

 his beliefs, in preference to even the most vivid recollections of 

 his dreams. 



The Lunatic Pauper who regards himself as a King, the Asy- 

 lum in which he is confined as a Palace of regal splendour, and 

 his Keepers as obsequious attendants, is so "possessed" by the 



* Thus, in a recently recorded cn^e in which sight -was imparled by opera- 

 tion to a young woman who h^d been blind from birth, but who had never- 

 theless learned 10 work well with her needle, when the pair of scissors she had 

 been accustomed to use was placed before her, though she described their 

 shape, colour, and glisteiai"g mttallic chara ;tcr, she was utterly unable to re- 

 cognise them nssriFsrrs until ^he put her finger on them, when she at once 

 named ihem, laughing at her own itupidily (as she called it) in not having 

 m-adc them out before. 



conception framed by his disordered intellect, that he rf'ow project 

 it out of himself into his surroundings ; his refusal to .nlmit the 

 corrective teaching of Common Sense being the very essence of 

 his malady. And there are not a few persons abroad in the 

 world, who equally resist the teachings of Educr'ted Common 

 Sense, whenever they run counter to their own preconceptions ; 

 and who may be regarded as — in so far — affec ed with what I 

 once heard Mr. Carlyle pithily characterise as a " diluted In- 

 sanity." 



It has been asserted over and over again, of late years, by a 

 cl.ass of men who claim to be the only true Interpreters of Nature, 

 that we know nothing but Matter and the Laws of Matter, ami 

 that Force is a mere fiction of the Imagination. May it not be 

 affirmed, on the other hand, that \^■hile our notion of Matter is a 

 Conception of the Intellect, Foree is that of which we have the 

 most direct — perhaps even the only direct — cognizance? As I 

 have already shown you, the knowledge of Resistance and ot 

 Weight which we gain through our Tactile Sense is derived from 

 our own perception oi exertion ; and in Vision, as in Hearing, it 

 is the Force with which the undulations strike the sensitive sur- 

 face, that affects our consciousness with Sights or Sounds. True 

 it is that in 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 in- 

 directly the undulations by which .Sound is propagated, and in 

 proving to our Intellect that the Force concerned in the trans- 

 mission of Light is really enormous.* 



It seems strange that those who make the loudest appeal 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 Common 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 inti- 

 mate connection between Cause and Effect, as it is in regard to 

 the existence of an Eternal World ; and that consciousness arises 

 to every one out of his own sense of personal exertion in the 

 origination of changes by his individual agency. 



^f ow while fully accepting the Logical definition of Cause as 

 the " antecedent or concurrence of antecedents on which the 

 Effect is invariably and unconditionally consequent," we can 

 always single out one dynamical antecedent — the Power which 

 does the work — from the aggregate of material conditions under 

 which that Power may be distributed and a]>plied. No doubt 

 the term Cause is very loosely employed in popular phraseology ; 

 often (as Mr. Mill has shown) to designate the occurrence thr't 

 immediately preceded the effect — as when it is said that the 

 spark which falls into a barrel of gunpowder is the cause of its 

 explosion, or that the slipping of a man's foot off the rung of a 

 ladder is the ciuse of his fall. But even a very slightly trained 

 Intelligence can distinguish the Power which acts in each case, 

 from the Conditions under which it acts. The Force which 

 produces the explosion is locked up (as it were) in the powder ; 

 and ignition merely liberates if, by bringing about new Chemical 

 combinations. The fall of the man from the ladder is due to the 

 Gravity which was equally pulling him down while he rested on 

 it ; and the loss of support, either by the slipping of his foot, or 

 by the breaking of the rung, is merely that change in the 

 material conditions which gives the Power a new action. 



Many of you have doubtless viewed with admiring interest 

 that truly wonderful work of Human Design, the Walter 

 Printing IVIachine. You first examine it at rest ; presently comes 

 a man who simply pulls a handle towards him ; and the whole 

 inert mechanism becomes instinct with life — the blank paper 

 continuously rolling off the cylinder at one end, being delivered 

 at the other, without any intermediate human agency, as large 

 sheets of print, at the rate of 15,000 in an hour. Now what is 

 the Cause Q){ this most marvellous effect? Surely it lies essen- 

 tially in the Power of Force which the pulling of the handle 

 brought to bear on the machine from some extraneous .'ource 

 of Power, which we in this instance know to be a Steam-engine 

 on the other side of the wall. This Force it is, which, distri- 

 buted through the various parts of the Mechanism, really per- 

 forms the action of which each is the instrument ; they only 

 supply the vehicle for its transmission and application. The 

 man comes again, pushes the handle in the opposite direction, 

 detaches the Machine from the Steam-engine, and the whole 



See Sir John He 



' Familiar Lectu 



I Scientific Subjects.' 



