THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID AN APPEAL TO PHILOSOPHERS, $C. SfC. \ . , AN APPEAL TO PHILOSOPHERS, BY NAME,. ON THE DEMONSTRATION OF VISION IN THE BRAIN, AND AGAINST THE ATTACK BY SIR DAVID BREWSTER, ON THE RATIONALE OF CEREBRAL VISION. BY JOHN FEARN, ESQ. LONDON: PUBLISHED BY MESSRS. LONGMAN, REES, ORME, BROWN AND GREEN, PATERNOSTER ROW. 1837. CIIKI.SKA: PKIVTEU BY w. BLATCII, 23, EXETKR STREET. K-cyr / it CONTENTS. Page 1. Introductory Address ... ... ... ... 1 2. 7%e Ushering in of the Fact of Recross Vision 22 3. 5z> David Brewster's Pneumatology in the Eye 32 4. O/Yfo ,Zfathe Mind, the Philosophy of Language ; and, lastly, A Rationale of Cerebral Vision. The last mentioned of the works, here enume- rated, constitutes an entire New Department in Philosophy. Arid I confess holding this con- tribution peculiarly precious, inasmuch as it forms the terminating stage of my labors in the Science of Pneumatology, by its being the connecting link, of physical action, between the Percipient Mind and the Extended Things of the External Uni- verse. The necessity of the case, however, and not any other motive, has obliged me here to mention this nature and amount of Cerebral Optics ; inasmuch as the manner in which it has been met, by a Censor of the Press, who also happens to be pecu- liarly advantaged by Position in the Scientific Community, has roused me, after seven years 1 endu- v j[i DEDICATION TO ranee of this wrong, involving a virtual death to my literary prospects of every description, to seek justice, if it may be found, against the operation of Power unrestrained, a justice which, I feel confi- dent, is as vital to the honor of our Country in the face of surrounding Nations, as it is to the endurable onward existence of the Individual who thus so- licits it. As for the probability whether, or not, I view this matter rightly : The lapse of seven years, during all which additional time I have re-exa- mined not only the Subject itself: but, along with it, its unqualified condemnation by an Optical Func- tionary, who at least ought to be in his Subject ; It may be taken as of some weight that, I move forward with the following Appeal to Philosophers with even increased confidence in my Subject : While, I must certainly be fully aware of the con- sequence to my own reputation, if I should be found mistaken in my perseverance. This, of course, is not the place for me to assign the motives of the Onslaught which has in effect proscribed my philosophical existence. But I leave the motives to be judged of by the readers of the following Appeal. And I only here state LORD LANGDALE. IX that, such an amount of condemnation must have been viewed, by all Optical Functionaries, as both absolving, and on various accounts deterring, them from looking at all into my Work, to judge of it for themselves. And, accordingly, it has followed that the most death-like neglect has at- tended my labor; insomuch that, I am lost to my generation if I may not find justice at some hand. If it should be thought that the Subject at issue indicates rather the fitness of appealing it to an- other Tribunal ; especially, when we consider the Urbane Spirit of the Prince whose Auspices now head the proceedings of the Royal Society of this Country ; The answer to this is the fact that, the Objects of the Royal Society embrace no conside- ration of Pneumatological Science. And, even if it were otherwise, the Individual who here seeks redress has never been a Member of that Insti- tution; and, of course, is not entitled to its inter- ference, in any case. Thus cut off from all other succour ; it is certain that the Subject at issue, as well as its Author, must be lost if the Equity of my Country do not inter- fere to save both. x DEDICATION TO And here, My Lord, over and above the consi- deration of an appeal to Equity, abstractly takeri ; there is an important specialty in bringing this case under the Auspices of your Lordship. For, While it would be untrue to let it be supposed that I boast the honor of being electly known to your Lord- ship ; yet, my right, on every ground, to good society, when health has permitted of my availing myself of it, has brought it accidentally within my personal knowledge that your Lordship forms one of the extreme few, who in this Country possess any Tincture of Philosophy, as distinguished from mere Science, a distinction which renders your Lordship peculiarly fit to apprehend the nature, as well as the hardship, of my case. But, there is yet another specialty in the case ; which weighs still more in my mind : Which is that I have been collaterally informed, that your Lordship's Moral Nature is such as might be ex- pected to accompany High Intellectual Attributes. And it is this Attribution that has determined me, to throw my case upon the hazard of your Lord- ship's approbation. In order to evince my trust in this adoption, I here x desire to say that, if I had interest with any LORD LANGDALE. XI one, who possesses personal influence with your Lordship, I would not accept his proffered medi- ation : But, would abide f the issue of your Lord- ship's spontaneous decision, as to whether, or not, your Lordship will extend Patronage to my case. And, in expressing this, I may add that, a seeking of Patronage at all, is an event wholly new in my life, through nearly forty years of Philosophical speculation. To come now, My Lord, to the proximate ob- ject of my solicitation ; it is that, through your Lordship's Auspices, I may be commended to the King, to be graciously pleased to confer on me his Majesty's Nomination to that Order, which is appropriate for those who have labored much, and usefully, in the Scientific Community. As my case at present stands ; it is in the power of any Scientific Individual, possessed of that Order, to inflict a virtual death upon all my labors, of every kind. And, when called upon for any ex- planation, either of errors, or injurious imputations, to avail himself of the plea that, an unaccredited Writer has no right to a reply. And, under this re- volting shape of philosophical despotism, which in fact wields a power beyond that of Law, the most Xll DEDICATION TO important contributions to Science, no less than the most useless, must (over and above the wrong done to individual claims) be no better than a dead letter in the philosophical community. It is past denial, therefore, that nothing is left to save me from certain uselessness, and as certain despair, but that I should possess a sign of my Sovereign's approbation, as a bar to any such plea, on the part of any one, as that of being exempt from all responsibility when my literary destruction is effecting under the cover of such a proceeding. It is not my presumption that your Lordship's eye should light upon the details of the following Appeal. But, if any person should be assigned that office ; I cannot doubt, but his anticipation will be far exceeded by what he will see of usurped power to inflict bane upon the labors of an opponent. In fartherance of my plea for the honor of such recognition as I would thus attain ; I may ven- ture to allege that, One Third Part of the Mass of Original Matter, which makes up my Published Writings, might fully justify my hopes, if compared with the labors of any other Writer on Subjects, equally abstruse. While the fact of my never hav- ing entered into a canvas to be elected a member LORD LANGDALE. Xlll of the Royal Society; (in which, I suppose, I might have succeeded ;) is a proof that I have not been given to put myself forward, in any way, until the necessity of the case became urgent beyond all endurance. My Lord ; As a make-weight, in my very extra- ordinary case, I am induced to throw into the scale the following mention of some circumstances in my early life ; for a purpose which will explain itself as I proceed. Descended sufficiently well ; and of Parents whose Excellent Virtues I desire in this late record to embalm, out of gratitude for the example of honor which they set me ; I at a very tender age willed to commence life in the Royal Navy : And, among other changes, served two years a midshipman on the quarter-deck of the Royal George, a First Rate Man of War; which now, more than half a century, lies accidently sunk at Spithead. If this narration should serve no better purpose ; it will at least show that, in my cast to Philosophy, I have not ex- changed from any sordid bent : But, have always done homage to creditable aspirations. Nor did XIV DEDICATION TO I relinquish my first choice from any fickleness of affection ; until the termination of the then exist- ing war cast me, with many others, upon the world of chance. But, the reason of my thus trespassing upon your Lordship's notice this otherwise insignificant matter, arises from the circumstance that it was my lot to serve in the grand fleet when his Gra- cious Majesty served his Country in the same. And I have been among those who were present on duty, when his Royal Highness has visited my Admiral. This last mentioned honor, I am fully sensible, amounts but to a very slender claim to his Majesty's favor, or recollection. But it serves my purpose to found upon it a hope with reference to my present case. The fact is ; we had it in the Fleet that his Royal Highness was of a GenerousNature, and loved that attribute of fairness which so peculiarly marks the character of our Country. And I do not believe that the intercourse of the world has made His Majesty throw off this feature of his early nature. Hence, I have been led to cherish a hope, that the King would not turn a deaf ear to the hard case of one who has had the honor to serve in the same fleet with his Majesty ; LORD LANGDALE. XV more especially, when I reflect on the time, near sixty years, that has elapsed ; and, how few of the gallan spirits of that day now remain, to share of good at his Majesty's hand. And, I trust it adds to this plea, when I state my transition, from a Com- petitor for Naval Glory, to an Aspirant after Phi- losophical Attainment: And this, as it should seem, led by the finger of Providence; since Providence, and not my forecast, or wish, brought it about. And now, My Lord, the Object of my solicitation for your Lordship's Patronage is expressed. And all that I would presume to add is to express that, a manifestation of your Lordship's Sympathy with my cause would prove a tower of strength to my saving : Since it is certain that your Lordship's High Station in the Community; and Philosophical Competency ; and Moral Nature; form, together, a Warranty to the World, that any such case, if protected by your Lordship, must have justice on its side. One consideration, indeed, remains to be thought of, here ; Which I would presume to name : Which is that, if it shall please Almighty God to permit ; I have yet more work to do, and part of which has some years been in a state of advance- XVI DEDICATION TO ment. But, My Lord, I believe no human forti- tude could continue to labor on, under the depres- sion which I have encountered. And, hence, I have only the prospect of being obliged to destroy, what I must not leave partly done to the hazard of being misapprehended. This prospect, indeed, presses on my mind. But, it is for me to pray that the Will of God be done. My Lord ; When an impartial Posterity shall come to adjudge this case ; I hope it will have to acknowledge that there was at least ONE Contem- porary Spirit that did sympathize with it. But, if it should prove otherwise ; then, it is for me duly to acknowledge that, I have no special claim upon your Lordship, other than that which I have coined out of my Estimate of your Lordship's Na- ture. And all, then, that is left for me, is to ex- press the irrepressible feelings of outraged Human Nature. My Country has been to me an unfeeling Step-mother. I owe Her, indeed, for the common protection of Her comparatively excellent laws : And, I hope, I have not been insensible to the debt. But the account is not equal. More than One Competent Critic has declared, in More than One Science, over and above that of Vision in LORD LANGDALE. Xvii the Brain, that I have presented Her with Things which She will accept when I am beyond the feel- ing of thank. And, in reward of this, She has left me to linger on, a living death : which Al- mighty God, alone, can give me heart to support : and, under an incapability of following that Course which has long been identified with my tolerable existence. And now, My Lord, With more pain of re gret for this trespass upon your Lordship's Philanthro- py than words would serve me to express ; I have the honor to subscribe myself With Profound Respect, Your Lordship's Most Obedient Humble Servant, JOHN FEARN. THE APPEAL. To THE FOLLOWING named Gentlemen, in- dividually considered; This Appeal is, with allre- pect, addressed by the Author. AND, DULY FIRST; To THE BRITISH FEMALE ASTRONOMER, MRS, SOMERVILLE. And, to the others in Alphabetical Order : with due apologies for the unavoidable omission of their Additions ; namely, PROFESSOR AIRY, Astronomer Royal ; PROFESSOR BABBAGE ; BELL, SIR CHARLES ; BAILY ; BAR- LOW ; BEAUFORT ; BAUER ; BLAKE ; BRIS- BANE, SIR THOMAS; BROOKE, A.C. ; CHRISTIE; COLBY ; GILBERT ; DOLLAND ; IVORY; HERSCHELL, SIR JOHN; DR. ROGET, one of the Se- cretaries of the R.S. ; SABINE ; LUBBOCK, SIR JOHN; PEACOCK, THE REV. GEORGE; SHEEP- SHANCKS, THE REV. RICHARD ; SOUTH, SIR JAMES ; WILLIS, THE REV. R. AND, EQUALLY, To ALL OTHER BRITISH NAMES OF THE SAME CLASS; in case any such have been unintentionally omitted above : Whose Moral Responsibility to their CONTEMPORARIES, and to POSTERITY, is INCLUDED, WITH THAT OF THOSE WHO ARE NAMED. GENTLEMEN. ' GENTLEMEN. As IT IS MANIFEST THAT, TAKEN COLLECTIVELY, You CONSTITUTE, AT THIS moment, the Effective Genius of British Optical Philosophy : And, as it is certain that the generations of men, who shall come after us, will require at your hands what has been done for the interests and honor of Optical Science, under your united aus- pices: While it has become, alike, my duty, and my resolve, that this Appeal, together with its scien- tific results, shall go down to its future judges, in- corporated along with other works, whose nature shall prevent the present Subject from being com- paratively locked up in the Archives, or Contri- butions, of the Single Science in question : It is with peculiar propriety that I address you on the Proofs, and Philosophical Consequences, of the dis- covery of a Visual Mechanism, and Process, within the Head, a Subject which it has formed a ma- terial and arduous portion of my life's labor to substantiate: But which has, since then, languish- ed in obscurity, a dead letter in philosophy, dur- ing a portentous period of no less than SEVEN YEARS, owing to a Cause which will be explained in the course of the following statements : but, which could not have thus operated unless it had found an aspect, or a tacit supposition, of a VIRTUAL SANCTION in the mere fact of your total silence with regard to the existence of any such thing. In noticing this silence, however, I by no means intend to impute to you any unfit neg- INTRODUCTORY ADDRESS. 3 ligence; inasmuch as it is certain that, owing to adverse health, and other untoward circumstances, I have never forwarded Copies, of my Treatise on the Subject, to by far the larger number of the Names whom I have now the honor to address. And, I deem it very probable that many of you are not yet aware of the existence of the Work : and, far less acquainted with its nature, or contents. And, here, I expressly provide that, I do not address you as Members of any Corporate Philoso- phical Institution. Which, if done, I am aware, would be irregular ; and such as could not be an- swered by an official functionary of any such cor- porate body. But, I address you as Individual Members of the Human Community atlarge. And I hardly need say that, you owe to this Tribunal a Paramount Duty, over and above that of any spe- cial corporate office, to which any of you may belong. And, now, that the Public Mind is altogether surcharged with the proceedings, and the public merits, of all our Corporate Institutions; I may, with peculiar force, put the question, If it shall be your election, that your Names shall go down to Posterity as having sanctioned, what I can here only designate as a, to me, most bane- ful Mis-view, publicly uttered by an Authority under the sanction, and advantage, of being a distinguished member of your own order. As for the Case, in other respects, of the Individual who thus solemnly throws his Cause upon your Justice; it is, certainly, a most peculiar one. And here it is proper I should intimate that, in my 4 INTRODUCTORY ADDRESS- not adding to my name the Honorary Letters which denote a Writer as being a member of the first Scien- tific Society in the Realm ; I am not to be viewed as undervaluing that Distinction. The general state of my health, during forty years: and, still more than this, the untoward fact that the Science of Pneumatology, in which I have exhausted my life, is not one of those that are comprehended among the departments acknowledged in the provi- sions of the Royal Society : both these causes have always prevented my going into a canvass, for the honor of writing myself a member of that illustrious body. But, under this unavoidable disadvantage ; I will here put a case in point, for the favor of your consideration. Suppose a Foreign Stranger, from some far-off country, as if it were Central Africa, were to visit your shores ; and, were to bring with him an ef- fective cargo of some New Department of Science. Let this supposed Department be no less than a Rationale of the Physical Intercourse between the Percipient Mind and the External World. In this supposed case; which, in fact is, with a wonderful juxta-position, no other than the case of the individual who has now the honor to address you ; What would be said, if your whole Collective Body were to draw up ; And, standing upon the Privilege of your Monopoly in the office of awarding the merits of scientific men, were to proclaim your rejection of the offering in question, UPON THE PLEA THAT IT CAME NOT FROM A MEMBER OF YOUR COMMUNITY ? In the present hour ; if such a blazon of illiberality were pro- INTRODUCTORY ADDRESS. duced to the astonished world ; I may ask, What would surrounding contemporary nations say, on beholding such a spectacle? But, far beyond the Sentence of rhe present generation ; What would the indignant Spirits of Posterity say, of such a manifestation that, NOT THE WEAL OF SCIENCE ; but only elevation, or self advantage; was the actu- ating principle in the highest of our Philosophical Institutions ? I trust that this supposed case; Nay, indeed, I may truly say, THIS ACTUAL REAL CASE ; presents a call upon your Equity ; and, also; upon your fame, and best policy ; which cannot fail to find a fit response in your own bosoms. I, indeed, have a fearful weight of interest; no less than a. whole life's labor, and hopes, depending upon your decision, to award, or not, a Sentence on the Case. And, I appeal it to You, "under Heaven. And, if need shall be, to Heaven above you. And here, as it is my design to comprehend, within the brief compass of. this Appeal, a MINIA- TURE COMPENDIUM OF THE SCIENCE OF PNEUMATOLO- GY, as it is now newly arising from an explosion of a by-gone Scheme of the subject ; and the Ad- vent of which is comprised in a Demonstration of the mutual interlimitations of our Sensations of COLORS, at any time when MORE THAN ONE uniform sensation of color co-exists in the Percipient : which fact, of a plurality of colors, is the usual case in the daily business of our visual intercourse with the External World. Which purpose, of supplying a Compendium, I shall here execute; in case this may prove the last contribution which the hand of Time shall permit me to offer to mycontemporaries. 6 INTRODUCTORY ADDRESS. And, with the hope that the thing proposed MAY RESUSCITATE an interest, or beneficial curiosity, in my Countrymen, to examine the nature of a New Scheme which, at the least, is of a complexion infinitely different from that which is exploded; and which had long wearied out the patience, as well as destroyed the confidence, of Englishmen. In exedution of this design, therefore, I shall present the subject with a description of the earlier links, of the chain of my life : Although, in so doing, I must mortify my pride, by proclaim- ing my want of all pretension to scholastic advan- tages, or honors ; or, even, so much as to the merest smattering, or initiation, I may premise here, however, that I would not have submitted myself to this humiliation, but from a conviction that the fact involved Wears, with very momentous effect, in its application to the PHILOSOPHY OF THE MIND, a matter which will explain itself as I proceed ; and which, I suppose, constitutes a valuable present to philosophy at large. The fact of my Case in question is that, upon my relinquishing a self-chosen course of life in the British Royal Navy ; I was, together with many others in the same case, by the termination of the war, and the occurrence of peace, in the year 1783, set at large : And I thereupon bent my way to afar distant region of the world : Where, at a very early age, in pursuance of my Maritime Profession, I had command of a Ship in several enterprises ; and, amongst others, in a Voyage through the Pacific Ocean. In the course of which last, I made the accidental discovery of some small Islands, INTRODUCTORY ADDRESS. 7 and extensive shoals; an account of which I duly communicated in a proper quarter ; and, which are since laid down, in the charts of those regions, as minute features of the earth's surface. The princi- pal addition to my stock of knowledge, laid in dur- ing that voyaging course, indeed, was in an ex- tensive and varied witnessing of SAVAGE LIFE, a field, however, in which a Philosopher may gather very valuable materials for his purpose. Having followed this maritime life, some years; I was, at length, induced to take up a very differ- ent course of action, in occupying a position in the Interior Regions of one of those Lands: in which situation, I was in a peculiar degree cut off from all but some very rare occasional intercourse with European life, or Civilised society. The intent of my recording these changes, of pursuit and of situation, is, as I have already intimated, their bearing upon the present state, and I trust the ad- vance, of Mental Philosophy. Which department of knowledge, undeniably, is by far the most important pursuit for the interests of our Species, both with regard to here, and to hereafter, pro- vided only that the Subject has been ; as I now confidently proceed upon the conclusion that it HAS been ; reduced to the stable form, and foun- dation, of a Strict Analytical Science. In pursuance, therefore, of this last mentioned conviction; I have NOW to observe that, the intel- lectual situation of any person, who has attained a NATURAL MATURITY OF UNDERSTANDING, before his mind has begun to be tampered with by the Schemes of Philosophy, both Ancient and Modern, 8 INTRODUCTORY ADDRESS. which have been, at various times, exhibited for the acceptance of mankind, must be far more competent to the task of judging between conflicting Theories, than if his mind had been vitiated by imbibing this, or that, Scheme of the Subject before it had attain- ed natural strength to digest the sound, and reject the unsound, speculations of his Teachers, Now, this solitary advantage, if such it is, I have certainly, and most largely enjoyed, under ' the want of every sort of Scholastic preparation. And, it is upon this plea alone that I ground my prin- cipal pretension to the philosophical consideration of my contemporaries. In this my lone and long seclusion, and unfledged state with regard to the Wisdom of the Schools; it happened that I possessed ONE Precious Guide, in posses- sing LOCKE'S ESSAY ON HUMAN UNDERSTANDING; a fortunate accident, which gave to my mind its first cast to wards Philosophy. For the rest; I sup- pose, I had some natural bent to the habits of re- flection. Which germ, however, I think, might never have expanded into any material fruits if, instead of being situated as I then was, I had been in the habits of bustling life; and, to a laving down of abstract thoughts, in the daily intercourse of civilised society. As it was ; the actual tenor of my life was nearly on a moral level with that of the wild ani- mals which were in fact my neighbours, and ac- quaintance, in the sylvan region which I then occu- pied. My daily amusement, during a series of years; (for the effecting of my pecuniary fortune INTRODUCTORY ADDRESS. 9 went on almost of itself;) was that of riding, frequent- ly, upon an elephant, or on horseback ; and inva- ding the repose, and disturbing the life, ofthe Wild Boar, and the Buffalo, in their lairs : Together witha varied, and most unsparing, slaughter ofthe lesser animals which Providence had subjected to my truly savage propensity. This life, to be sure, was the boasted life of a SPORTSMAN : Although it was, certainly, no sport to the ill fated Things which were slaughtered ; not as if it were by the Tiger, in order to allay the cravings of his natural appetite ; but, because it was, in fact, exhilirating to the spirits : And, very often, bore some sem- blance of war, in the frequent danger of en- countering enraged and formidable opponents. Curious it was, that, in the course of such a life as this, I found a strong and irresistible bias to- ward MENTAL PHILOSOPHY. For which, however, there can be no doubt, I was indebted, in part, to the fact of my embibing the Spirit of Locke's cele- brated Essay. Certain, at least it is that, in my solita- ry sylvan course of barbarous existence, I found in the real and apalling forms of surrounding Nature, a true substantiation of the fancy of a Writer who had owed as little to teaching as myself. "TONGUES IN TREES: BOOKS IN THE RUNNING BROOKS. "SERMONS IN STONES; AND GOOD IN EVERYTHING." Here, by the way, justice to a much-wronged Philosopher calls upon me to avow, concerning the Pneumatological Speculations of Locke, that I derived from them great and impelling benefit 10 INTRODUCTORY ADDRESS. and obligation. It is true, the philosophical course of our illustrious countryman cannot be defended against the charge of being frequently inconsistent with itself; and, with vaccillating, to an extreme degree, in the would-be logical tenor of his reasonings and illustrations. But, in the BET- TER views which he entertained, however they were mixed up with the alloy of his inconsistencies, he has taken his stand upon a rock which can never crumble under his feet. Accordingly, therefore, I have always, from the beginning, yielded to him my assent, and adhesion to his better grounds. And, in fact, my own stated Laws of Primary Vision, which are ALL IN ALL IN PNEUMATOLOGY, are but an ANALYTICAL DEVELOPEMENT, AND DEMONSTRATIVE RATIONALE, of his 'assumed, though vague, and in that form UNAVAILABLE GROUND, where he affirm- ed the SIMPLE FACT that, COLOR (by which he meant no other than that SENSATION OF COLOR) CAN- NOT BE WITHOUT EXTENSION. The work of an after generation; that of uttering animadversions upon, and holding up to contempt, the DROSS of Locke's Essay ; with intent to invali- date the gold of his better views; was an act of no more difficulty, than it was of praiseworthy merit. And, although it has well served its intended pur- pose, during a long era, in a politic manifestation of metaphysical opposition ; I have, for my own part, always proclaimed my due gratitude to the merits of the English Philosopher : and this, whe- ther, or not, he be supposed to have borrowed, from another writer, some important features of his doc- trine. At the same time; it is certain that, I am not INTRODUCTORY ADDRESS. 11 either his disciple, or his follower : Because, I have differed from him, no less than infinitely, in several of the most important features of Pneuma- tological Science ; as a single instance of which, I may here mention that of our two opposite, and incompatible, respective schemes of the CATEGORY OF RELATION: He following the Aristotelian Scheme of the subject : While I have suggested, and largely elaborated , a Scheme of COMBINED RELATIVES and RELATION ; which Subject occupies a very ex- tensive, or rather comprehensive, feature in my es- timate of the STRUCTURE of the HUMAN INTELLECT. There is one fact, of sufficient notoriety for its truth ; and, which is manifest in its operation upon public interest, orrather in producing a want of pub- lic interest, and a deplorable apathy, in the case of Cerebral Vision : And which, therefore, I must duly place in the view of all readers of the Sub- ject, with intent to suggest, and to urge, the IRRATION- ALITY of the thing ; even though we should grant the MARKET wisdom displayed in it. The mischievous fact, to which I thus call attention, is the general opinion that Vision in the Head, if it be proved, is not a Science which can produce ANY MARKETABLE benefit to mankind. Against this way of reasoning, however, I may state at least TWO very cogent arguments. First. One should think that no philosophic mind can hold Cerebral Vision to be valueless, from its present want of commercial products : because, 12 INTRODUCTORY ADDRESS. from the probability that a Science of so comprehen- sive a scope must, one day or other, bear upon various commercial products : and, even, without bringing in this stimulating consideration ; no philosophic mind would deem it creditable, to human reason, to argue within so contracted a sphere. Besides these considerations, moreover, I have here to urge the fact that, Sir Isaac Newton, and his illustrious associates, have manifested a plenitude of interest in the subject of vision in the brain, an event in the history of the subject that cries out upon my thought of a Gene- ral Apathy on the Advent of a Province of Philoso- phy which had been so ardently sought, and in fact anticipated, by those illustrious persons. But, Secondly, here. There is One Commercial Consideration, to bementionedinthisplace; which probably may ; although, also, it probably may not; present an object ofmarket interest in Cerebral Vision. And, I shall at least announce the thing here, in case any Optical Philosopher will afford it his attention ; as it is not in my power to follow it farther than this hint. But, even, if this matter should be productive of no commercial fruits; still, the very fact of its occurrence affords at least an indication that, other fruits of the same kind may grow from Cerebral Vision. The matter, to which I thus allude, is related in the course of an investigation ; the details o t which form a "Second Supplement" to my Rationale, under the title of "The Sensorium In- vestigated as to Figure, by a Course of Pressures INTRODUCTORY ADDRESS. 13 on the Eyes." And, the fact itself is that to which I have been led to assign the name of " The Sen- sorial Aberration of the Eyes." And some notion of this fact may be gathered from the following extract from the Rationale. " The most considerable, of these remaining dif- " faculties, is the WANT OF A TOTAL coincidence, la- " terally taken, of the impressions from both the " cranial eyes, in their respective discharges "upon the Sentient or Percipient Mind: Or, in "other words, the difficulty consists in the fact "that, the Sensorial Field, taken in its lateral * c extent, is not wholly common to impressions "from both eyes ; not, even, when the eyes, and " the pressures, are so disposed as to produce " the greatest practicable approximation to a total " coincidence." It is not necessary to insert more of these extracts, as the Rationale itself may be consulted by those who wish it. But, there is much more in it, on the same subject. And the application, which I shall here make of this fact, is to call attention to the existing stale of the Art of making , Binocular Telescopes. From some cause, or other, those in- struments are found useless, when applied to Astronomical Purposes. Now, the question here is ; Could it be possible to improve Binocular Teles- copes, for observing the Heavenly Bodies, by adapt- ing those instruments to the Lateral Aberration of the Sensorial Color Images, as I have above described it ? And, having thus suggested this hint ; I shall leave the matter to others, if they choose to consider it farther. In fine, enough ap- 14 INTRODUCTORY ADDRESS. pears to justify, fully, a hope that the Department of Vision in the Brain may have marketable pro- ducts; altogether besides its Pneumatological, and other Philosophical products. There can be little doubt, but, when Sir Isaac Newton FRIED the Optic Nerves ; and, tried other experiments with a hope to gain light on the subject ; he imagined that some discoveries, useful to practical science, might come forth from such labors. By the way; I notice here that, in the Rationale, I suggested a hint, in what way a variety of Toys might be constructed for amusement, upon the principle of Two- Eyed Vision. And, since the pub- lication of the Rationale, there are actually several such Toys selling in the shops. And, as it is certain that neither Newton, nor any other Writer, has ever admitted the fact of Two-Eyed Vision in the case of Man ; or, in that of any Animal whose eyes stand in front of the head ; it seems hardly to be doubted, but the Toys in question are such as I suggest- ed. And here, I merely add, that a variety of other Toys, of a very amusing character, might be contrived ; besides those which I have seen, as above mentioned. And, perhaps, some of these might not be altogether devoid of scientific utility. At the same time, nothing can be more wonder- ful than the denial, by Opticians, of Two-Eyed Vision ; since we have only to apply our hand, edge wise to theNose; and we shall instantly be con- vinced that the Grandest, and Most General, Mode of Vision, is that of seeing One Half of our Whole INTRODUCTORY ADDRESS. 15 Field of Objects with One eye ; and the other half with the other. The mistake in question is so equal- ly surprising, and important for the mischief incurred by its admission hitherto in all optical speculations; that I deem it duly effective to men- tion it repeatedly, in case some readers might other- wise suspect that, in my optical writings, I have fallen into some mistake inthe matter. But, certain it is that, not only Sir Isaac Newton ; but, also, va rious other Writers on Optics; and Medical Authors in discourses of the eyes; down to the latest date; have severally assumed that, we employ both eyes never but as one Organ. And that, the only use, and Final Causes, of our having two eyes, is in case that the sight of one of them should, by any accident, be destroyed. The Oversight in question is, certainly, the most extraordinary, as it has also been the most detrimental to the advance of Optical Science, of any in the whole history of the subject. And it is, even, the more wonderful from the certain known fact that, if perhaps twenty persons look, intention- ally, at any object with both eyes; not one of the whole twenty can see it with both, because some accident, or a mere acquired habit, has rendered one, or other, of their eyes less effective than its fellow. And, to crown all this ; it is a certain fact that, many persons have made the discovery that they had been blind of one eye during several years, without their ever having suspected their defect. Wonderful, it certainly is that, such as I have now described has been the past state of our 16 INTRODUCTORY ADDRESS. knowledge of our visual constitution. Not only all the Vulgar Mass of our Species; but, ^also, all our Philosophers, in their teachings of the subject; confidently believing that we see objects with both eyes. While no truth in Science is more cer- tain than that, our Grandest Mode of Vision con- sists in viewing the Creation, in any present Unli- mited Field of Vision, One Half of it with One Eye, and the Other Half with the other. But I pass on now, to a very different subject of Consideration. Over and above the untoward operation of the general prejudice, that the Advent of a Science of Vision in the Brain can be produc- tive of no marketable fruits, or consequences, in the community; there exists yet another general opi- nion, or assumed scientific principle rather, in the Optical World ; which is, to the last degree, hostile to the reception of Cerebral Vision. The mischievous supposed principle, to which I now allude, is the assumed Principle of the Visible Direction of seen objects from the eye. The discussion of the merits, and claims, of this So-cal- led Principle, therefore, must be the business of the present section ; in as much, as it is a stumbling block in the subject: Although, fortunately, notwithstanding the deep root it has attained in the general opinion, there is no Proposition in Geo- metry whose truth is more rigorously demonstrable, than is the falsehood, or unreality, of the assump- tion that we see External Direction. In order to introduce the merits of the thing ; I must here ad- vertto the CHANGE, which is introduced into the INTRODUCTORY ADDRESS. 17 nature and division of the departments of theScience of Optics, by the Advent, or Accession, of Cerebral Vision. First, therefore, I observe that, Since the late accession to thesubject, the Science of Optics stands divided in to two great, and vastly different regions or departments. One of these is EXTERNAL (or what I have called LUCERNAL) Optics, namely, that which comprehends the incidence of rays of light upon the retina of the Eye. The other, comprehends the Nervous Mechanism which is situated behind the eyes: And this last I have, consequently, deno- minated Cerebral Optics. Now, there is no denial here, that, in the Department of External or Lucernal Optics, there is a real and true Principle of the External Direction of objects from the eye. This, in other words, is the principle of the converge essence of the rays of light ; and, of their crossing each other, until they ultimately fall upon the Reti- na. And, it is certain that, the retinal impression, from any point, of any external seen object, is op- posite, in a straight line, to that point of the exter- nal object which reflects the ray of light upon the retina. But, while all this is here fully granted, and provided for ; the grand consideration that is vital to the nature of Optics here, is that, although the external direction of the object is a true prin- ciple ; still, it must be remembered that, we never SEE this External Direction. It is an external known fact, from deduction, a fact of calculation ; but it is never a fact of vision. So far am I, indeed, from being entirely alone jg INTRODUCTORY ADDRESS. upon the ground now asserted ; that there are, at least, two other writers who have taken up the same ground. The first of these whom I shall notice here, was Mr. Crisp : whose Treatise, notwith- standing it contains some points of considerable merit, has found its way to oblivion. Mr. Crisp asserted that, the retinal place of a seen object is its relative place on the retina, compared with the re- tinal places of other objects imprinted on the retina, and seen at the same time. And I consider him as having been aware of the real fact of the subject, in this instance. But, this fact evinces, beyond all question, the grand truth that, it is the MIND, from behind the eye, that thus sees objects in their relative retinal positions, in the case of any field of objects that are seen at any same time. The next other writer, who has': taken "^up the same ground, is no less a reputed Optical Adept than Sir David Brewster, in his announced pro- posal to the world, expressed in his ' ' Natural Ma- gic" to show that all Visible Objects are no other than the impressions of the Rays of Light that are PRICKED upon the Tablet of the Retina. Thirdly. To be classed here, so far, with the Two Writers already mentioned, is the case of the Individual who has now the honor of addressing you. But, with regard to my estimate of the sub- ject; a most momentous distinction is here to be made, between the fact of our perceiving objects in their relative positions on the Retina, and any supposition that any true identical or immediate ob- ject, which we ever perceive, is an impression on INTRODUCTORY ADDRESS. 19 the Retina. The certain contrary of this, or the grand pneumatological fact is that, the only objects we ever perceive are our own sensations of colors, de- marked and interlimited ~by t each other, in the mind. But, since I began to write this Appeal, I have become possessed of a fact of the most conclusive importance, as bearing upon the subject at is- sue. An American Lady, Mrs. Griffiths, has addressed a short communication to Sir D. Brewster, which he has inserted in his Journal for January ', 1834: in which, that lady relates having, one morn- ing, with the yet unopened eye, seen the Retina and its vessels, presenting a most beautiful spectacle. And Mrs. Griffiths, very cogently, remarks that the THING WHICH SEES THE RETINA, MUST BE POSTERIOR TO THE RETINA. This very novel and surprising re- velation of sight is, most certainly, of itself alone, decisive of the fact that we NEVER SEE the Im- pressions of Light upon the Retina. And, to confirm this ; and to stamp it for a Principle in Optics ; Sir David Brewster, in a paragraph at the end of Mrs. Griffiths' Paper ; while he objects to some of the minute features of her description;/^?/ assents to the important fact in point. And it ap- pears that both he, and others have seen the same revelation of the retina, with its vessels. Now, While this fact proves, for ever, the annihi- lation or explosion of the heretofore asserted Princi- ple of the Visible Direction of Objects; it seems wonderful that Sir David Brewster does not appear to have drawn from it the certain annihilation of his projected Pneumatology in the Eye \ Bat we are to c 2 20 INTRODUCTORY ADDRESS. remember that Sir David had commenced his Project in the year 1832 ; Whereas, Mrs. Griffith's important discovery did not occur until 1834 ! Can it, then, be doubted that, after this decisive disco- very, I go forward in the confidence that the sup- posed Principle of Visible direction is an exploded Principle. And that the truth of a Science of Vision in the Head is established by the single fact of Mrs. Griffith's discovery, alone. To proceed, here, it is plainly to be understood that, when the nervous mechanism in the brain has called up, or occasioned, in the mind, a visual pic- ture; the various objects in this picture will possess relative places, (with respect to all the other objects seen at the same time,) corresponding with the re- lative places of the various impressions upon the eye or retina, and which retinal print was the physical occasion of our having the vision in question. And, attending to this view of the subject, Mr. Crisp was right as to the initial or precursory optical fact. But, certainly, he had no guess, whatever, as to the Ultimate or Pneumatological Fact of Vision. Sir David Brewster, on the other hand, assert, that, not only the retinal impulses from light ; but, along with these, the Color Images of the Mind, themselves, are part of the Furniture of the Retina of the Eye. Whatever may be thought of the res- pective claims of the two Schemes in question; it is certain that no less than the distance of infinity, at least, exists between their two respective natures. To afford here an Analogy of the process of Vi- sion, as it exists in Nature ; I shall transcribe INTRODUCTORY ADDRESS. 21 that which I have supplied in my Rationale, in treating of the " Principle of Coincident Images/ 9 and, in other parts of that work. " Over and above the gift of Two Cranial Eyes, " man has been, by his Adorable Creator, endowed " with an Internal Central Organ, which performs " the Office of a Third Eye by being the Com- " mon Recipient of impressions propagated either '' from one, or from both, of the external eyes. And " the Mind, in her Chamber of Percipience, steers " with regard to external objects on the sameprinci- " pie on which the mariner steers by his compass. " Thus the two cranial eyes are analogous, in prin- ' ' ciple and situation, to two magnetic compasses pla- * l ced upon a ship's deck : while the third, or cerebral " eye, represents another compass placed in the ca- " bin below. And the mind, situated like the Cap- " tain Mariner in his cabin, knows, from consulting " the central eye, upon what point of direction the " body is steering : Although, the Mind no more " perceives any external object, nor yet any im- " print in the cranial eye, than the Mariner perceives, " (even in the vulgar import of the word per- " ceives ) the far off land, or haven, toward " which he is surely making his way." This Analogy I have again supplied here, in as much as I conceive it is strikingly true to the real nature of the subject ; and conveys, at a glance, a glimpse of the whole Grand System of Mechanism, by which we are, for our own benefit, cheated into a confident belief that we see the External World, which, most certainly, we never do see. Nor is 22 , TH E USHERING IN OF there, perhaps, any other knowable work of GOD, that calls more loudly upon our adoration of him. THE USHERING IN (for the present occasion) OF THE FACT OF RECROSS VISION. It is known that Sir Isaac-Newton has noticed the appearance of that Visual phenomenon, whichhelik- ened to the Spot in the Feather of a Peacock's Tail ; and which is occasioned by pressure, by the point of a finger, on the Angle of the Eye. This phenomenon he has recorded ; But, without having traced it to any result. And, indeed, the thing is no other than is known to every one ; together with other such phenomena, arising from blows, and other causes. And here it appears to be a most wonderful omis- sion, in the case of so vast a mind as that of Newton ; and this, too, at a time when he was bent upon obtaining any light on the subject ; that he never thought of trying TWO PRESSURES, SIMUL- TANEOUSLY, ONE On EACH EYE. HAD HE DONE so, but in a single instance ; in that instant, One of the Grandest, and Most Important, of all the Arcana of Nature had been revealed to him, by its flashing on his Sight : And, he would have been delighted on finding the reality of that Visual Mechanism in the Head, whose existence he had always firmly believed in ; and which, also, agrees in gross with the creed of all philosophers, both an- cient and modern ; the school of Reid alone except- RECROSS VISION. 23 ed : But, which he had not succeeded in bringing to light; although he practised many experiments with that view ; and, had actually fried the optic nerves, among other means for obtaining his purpose. The Grand Visual Fact, which would thus have burst upon Newton's view, consists in a display of the truth that, upon pressing the Outer Angle of the Right eye, we behold a Peacock's Feather situ- ated on the Relative Left side in the MIND, residing in its Sensorium in the JBrain : While, a similar pressure upon the outer angle of the Left eye occa- sions our seeing another Peacock's Feather, situated on the Relative Right side in the Mind : BOTH the feathers being seen simultaneously, in the presence of each other. Now, this most beautiful and astonishing exhi- bition ; and the tracing of its Rationale ; is that which has, by Sir David Brewster, been desig- nated the " PHILOSOPHY OF FOOLS." And this designation he has, as he thinks, justified by his turning the FACT of Two eyed Vision, into a supposed Case of the Vision of a single object, view- ed by a single eye. The Example of the Recrossed Feathers, now afforded, however, may be considered as a FIRST FRUIT, or leading crucial example, of Recross Cerebral Vision. But there is a consideration here, which we must not leave behind us ; and, which is that of an attempt on the part of Sir David Brewster to invalidate Recross Vision by means of introducing 24 THE USHERING IN OF an Extraneous Phenomenon into the example which I have just afforded. Thus, he says, in speaking of my labor : " If he had acted upon his eye-ball " with a greater pressure, an experiment not very " safe ; he would have found that the pressure was " propagated across the eye-ball, to the opposite " point of the retina; and, that in consequence " of two opposite points of the retina being acted " upon simultaneously by pressure on one point, " two diametrically opposite luminous images are " produced." Now, the occurrence, sometimes, of the two phe- nomena which he has thus described, is, indeed a fact. But the phenomenon which appears under the point of the pressing finger is not a peacock's feather ; but, on the contrary, is a longish narrow stripe, of a pale whitish brilliancy. But, what renders it strikingly an object foreign to the Pro- blem of Recross Vision, is the fact that, it some- times appears, and sometimes not at all: Whereas, the two peacock's feathers are as constant atten- dants upon the pressures, as a shadow is upon every- thing on which the sun shines. My Rationale will show that this extraneous phenomenon had not escaped my notice. And here, I conjecture that, it is occasioned by the Bony Socket of the Eye; against which the Eye-ball must be pressed, at any time when the pressure is strong. But, whatever may be the occasion of this sometimes intruding phenomenon : If Sir David Brewster cannot deny * ^ * (and, most certainly, he cannot deny,) that the feather which is seen on the Left side in the Senso- RECROSS VISION. 25 rium is occasioned by the Pressure on the Right Eye ; and, the feather seen on the RIGHT SIDE in the Sensorium is occasioned by the Pressure on the Left Eye ; then, it was unphilosophical in him to drag in a foreign object, to embarrass the problem. Accordingly, therefore, his attempt recoils upon his own judgment. It may be worth explaining here, that, if my conjecture, in this matter, prove true ; then, the foreign phenomenon, which Sir David Brewster has called in for the purpose of nullifying Recross Vision, is itself an example of Recross Vision. For, While a light or a moderate pressure, on the outer angle of the eye, occasions a feather to ap- pear immediately opposite to that pressure ; a hard pressure, on the contrary, by pressing the eye-ball against the opposite Bony Socket, obliges the Socket to occasion the Streak of Color, immediately under the point of the pressing finger. Here I am absolutely driven, in self-defence, to protest against the procedure of my Critic upon the Subject of my course of Pressures, a subject which 1 have supposed I might consider as being almost exclusively my own province. Nor, is my personal feeling ; nor yet my pretensions to use- ful labor ; the principal consideration in this case : Because the thing, to be here protested against, operates with great detriment upon the Public Mind, in misleading it from the investigations upon which Recross Vision is asserted. In that part of his Critique, above quoted, Sir David Brewster breaks out into the following censure of 26 THE USHERING IN OF my Course of Pressures on the Eyes: " Thus " disappointed by the perusal of the first sections " of Mr. Fearn's book ; we hoped to find some- " thing deserving of praise in his fifth and last " section, ( On Vision without External Objects,' " a subject very little studied, and one in which it 16 would be difficult to make numerous experi- " ments without stumbling on some useful, or im- " portant fact." Now, it is a little after this effu- sion that he utters the taunt, manifestly implying my being puerile in the subject, in my not having urged the Pressures to a more effective degree. And, he crowns the lesson, by the following asser- tion : " Hence, we explain all the phenomena " which he has described ; and many more which " have escaped his notice." It is said that men bear insult less patiently, than they do injury. And, I confess, I have suffered more of chagrin from the operation, in my mind, of the vaporing taunt in question, than I have done from reflecting on some of the blunders which bear importantly upon my Views. Would any one, who reads the flourish, at the expense of my labors, and with the obvious design to write me down as a novice in the matter, imagine that the extent of my Course of Experiments, in the De- partment of Pressures is, to the best of my belief; and, from all that my Opponent has said of his own experiments ; at least more than FIFTY TIMES the extent of his experimental course in the same department ? And, to render his weening the more astonishing ; he has, in the same part of RECROSS VISION. 27 his same Critique, accorded to me the following acknowledgement of the fact. Thus, he says, " The Optical readers of this Journal will recollect " that we had occasion to discuss the aiialagous " subject of the vision of impressions on the retina. " These impressions, however, were made with " strong light upon the retina ; whereas, Mr. Fearn " has occupied himself principally with the lumin- " ous circles produced by pressure on the eye-ball." Now herein is an express acknowledgment that, the extent of my Course of Pressures went the length of a " PRINCIPALLY." And here it is con- clusively edifying to PIT, against this recorded prin- cipally, the extent of Sir David Brewster's entry upon the same Department of Optics. His Cri- tique on my Rationale, I have already said, extends to about three whole pages of his Journal. And, besides this, he has read a Paper, of his own, also of about three pages in extent, before the British Association, on the Subject of Pressures : In the course of which last, he has described ex periments leading to THREE RESULTS ; not one of them bearing, (even in his own estimation,) upon Recross Vision. If he has ever moved farther than this, in the Department of Pressures ; I am ignorant of the fact. But, I think it is undeniable that it was my Rationale, in the year 183J, that first set him, at all, upon a Course of Visual Pres- sures. And yet, such is the extent of labor, in this department, of the Optical Functionary who has schooled me to this amount, on the Induction of Pressures. I may submit it to all honorable 28 THE USHERING IN OF minds, Whether this is not a mode of CRYING DOWN the labors of an Opponent, such as might be far more expected in the walks of lower avocations, than in the high paths of philosophy. The real truth of the case is that, so far has Sir David Brewster been from shewing me the way to perseverance in this department, that I have here, in order to warn others who may be induced to take up such experiments, that, although, I think, a course of moderate pressures rather strengthens the eye ; yet, I have more than once urged the pressures, both in mode, and in degree, so far as to bring on symptoms which gave me considerable disquietude for some time. And, I do not think that the degree of the presssure can safely be carried so far. Although, perhaps, the manner may be varied to some useful effect. But, there is a far other matter here, than the ween - ing boast described. For the truth is that the very phraseology alone, employed by Sir David Brewster, as already quoted, is a critical test of his utter darkness in Recross Vision, a darkness which is most won- derful when he had that Department laid out before his eyes in the Rationale. Thus, when he talks of my being occupied principally with circles produced by pressure on the eye-ball', he ought to have said, in the plural number, pressures on the TWO EYE BALLS IN CONCERT. And, although it is a most momentous Optical truth that, EACH EYE has its OWN PROPER MECHANISM for producing RECROSS VISION: (which recorded truth Sir David Brewster would have found, if he had but pressed upon EACH corner of a Single Eye:) Yet, he never men- RECROSS VISION. '29 tions any such thing as TWO simultaneous pressures, either upon one, or upon both eyes. The reality of Recross Vision is, I trust, now established upon the strongest ground of actual induction of phenomena, and of reasoning upon those phenomena. And thus, a NEW HALF, (as it may be called,) is added to the Science of Optics. A consequent demand for the employment of New Names is now requisite, in order to distinguish the two departments now in existence. And, accord- ingly, I have supposed it indicated to designate the One by the name of Lucernal ; and the Other by that of Cerebral Optics. I shall now advance, as speedily as circumstances will permit, to exa- mine Sir David Brewster's supposed refutation of my views in the Department of Lucernal Optics: this being the department which he has chosen, EXCLUSIVELY, for his purpose. But, previously to this, I am under a necessity to entertain a very different consideration. On the publication of my Rationale, in July 1830 : and being, I confess, impressed with a con- fidence in the thing, quite equal to that which I could repose in any mathematical process : I sent a copy of the work to Sir David Brewster ; whose position in the community, not only as an Optical Philosopher ; but, also, as being the Actuary of a " PhilosophicalJournal ;" rendered him peculiarly fit to take the matter into consideration. As such, I called upon him, not indeed for his criticism ; but for his recognition, as he truly says. Sir David Brewster was not slow to answer my call. And, 30 THE USHERING IN OF in his " Journal" for April 1831, he has pro- nounced upon my Work ; including, indeed, all my other labors, on every subject ; such a scathing of contemptuous effusion, as has perhaps never been surpassed, if ever equalled, in the annals of philosophical hostility. And, such was the over- whelming advantage which he possessed, in point of POSITION in the Scientific Community, that the exterminating Sentence, which he thus pro- nounced, fell like the bolt of heaven upon the work. For, although, at first, it began to move, as such an unpopular subject might be expected to do ; yet, from the appearance of the Critique in question, during now a lapse of Six Years, it has remained virtually as dead, as if it had never ex- isted out of the brain of its author. The Critique, which has wrought this virtual death upon my labor, is certainly of no ordinary composition. And, it deserves to be held up here, as a logical tissue of its own kind. In point of extent ; it does not occupy more than three whole pages of the " JOURNAL." And, yet, it contains a denounced bane upon a variety of my labors : And, so chastises my moral want of decorum, in my imputed, but falsely imputed, attacking of my betters in philosophy ; That, if I cannot find justice of iny Country under this shower of odium ; (enough, certainly, to scare all men from the hazard of holding literary communication with me ;) I can have no wish to lengthen out a life reduced to this predicament. What crowns the complexion of this Critique RECROSS VISION. 3} is that, it is written, not in a morose or ascetic strain ; but, on the contrary, in a bland and bene- volent tenor : the characteristic feature of which is a desire for my good; and, for my amendment, in order to produce this good. And, in the climax of its phi- lanthropy, it is most HIGHLY MONITORY ; and full of regrets that he is under the necessity to show that I am thus devoid of propriety, as well as of science. And here I trust that, his benevolent intentions; (of which, it will be indispensable that I should afford a specimen farther on ;) will not be lost to the subject; but will be duly appreciated, as an internal evi- dence of the SPIRIT in which the Critique was conducted ; more especially when it is to be taken into the account that the person, for whose amend- ment all this was intended, was an old man, who, in the course of nature, was past all improvement. But, to come now to the GIST of my CASE : AFTER SEVEN YEARS of my endurance of the pres- sure of Sir David Brewster's Critique ; during all which years an old man has been advancing nearer to his grave ; I now bring SUIT OF APPEAL to my Country, in the persons of her Optical Philosophers. And, remarkable it certainly is that, upon so long and slender a thread has de- pended the future existence of Cerebral Vision : for, if this thread had snapped, there appears little chance but it would have remained a dead letter under the condemnation of an approved optical functionary. And here, I hope, I have evinced a sufficient 32 OF SIR D^VID BREWSTER'S extent of endurance, especially when I urge that it has never been lightened by any sign of consideration on the part of its Author; although my published "Letter" to him, which forms a Third Supplement to my Rationale, has afforded to him an ample occasion to redeem the mistakes which have proved so effectively ruinous to my prospects. THE DEVELOPMENT OF SIR DAVID BREWSTER'S SCHEME OF VISION AND PNEUMATOLOGY IN THE EYE; AS CONTRASTED WITH VISION IN THE MIND, IN THE BRAIN. We come, now, to consider the UNFOLDING of the Scheme of Pneumatology, projected by Sir David Brewster, as already announced in the Introductory Address. In the course of bringing out this Scheme, in his "NATURAL MAGIC," he has expres- sed himself as follows ; " The affairs of life could "not go on, if the memory were to intrude its " bright representations of the past into the domes- " tic scene ; or scatter them over the landscape. " The two opposite impressions could not co-exist. " The same nervous fibres which are carrying from " the brain, to the retina, the figures of memory, " could not, in the same instant, be carrying back "the impressions of external objects from the re- PNEUMATOLOGY IN THE EYE. 33 " tina to the brain. But, so rapid is the exercise " of mental power, &c. &c." Now, in the effusion just quoted, we have it manifestly asserted that, Each of our Optic Trunks is a thing* precisely of the Same Mechanism, as that of our Rail-roads. And, accordingly, either of the Optic Trunks cannot convey two contrary progres- sive Trains of Carriages at the same moment : but, the IDEAS that are passing toward the brain must wait their turn ; while the opposite coming trains of IDEAS are occupying the road ! PHILOSOPHERS' OF BRITAIN ! before we proceed farther in this Scheme ; I would ask : Can it be the SAME GENIUS that has proposed this Rail-road Pneumatology ', that has also stigmatised Cerebral Vision with the Epithet of the "PHILOSOPHY OF FOOLS ?" But, to proceed. Sir David Brewster develops his Scheme as follows : " In darkness and soli- ' tude, when external objects no longer interfere "with the pictures of the mind." Here, then, we find an acknowledgement that, "pictures" of things are in the mind : Which, most certainly they are ; being no other than our sensation of colors, variously arranged. And, yet, in the Scheme in question, they are asserted as travelling out of the mind ; and this, in the same waggons, and on the same Railroads, which convey the retinal impres- sions. This enormous violation of the uncontra- dicted admission of Philosophers, that Sensation is an affection of a mind only, I shall have to notice fully in a future section on the dif- D 34 SIR DAVID BREWSTER'S ference between COLOR arid LIGHT. But, at pre- sent, it is enough to call attention to the assertion in effect, that the Thoughts of the Mind are con- tinually performing alternate voyages, from the mind to the retina ; and back, from the retina to the mind. And, consequently, that the mind and the re tina are, each ofthem, an Emporium or Store-House for the occasional deposit of our thoughts. Again; he says: "With persons of studious " habits, the mental pictures are much more dis- " tinct, than in ordinary persons." And he goes on, at some length, in the same strain. Again : He asserts as follows. 4< If it be true, " then, that the pictures of the mind, and spectral " illusions, are equally impressions on the retina;" (PICTURES OF THE MIND IMPRESSIONS ON THE RETINA!!!) u the latter will differ in no respect "from the former, but only in the degree of "the " vividness with which they are seen." THIS, THEN, GENTLEMEN, is the newly pro- posed Scheme of Pneumatological Science ; a pro- posal, not by an obs'cure or nameless pretender, who, if not accredited by titles of merit for actual attainments, one would confidently pro- nounce to be a charlatan in the subject : But, on the contrary, a British Functionary, of high and just reputation for services rendered in a cer- tain department of Optics. Now, As Sir David Brewster's Natural Magic was published in the year 1832 ; And, my Ration- ale of Cerebral Vision appeared in 1830 ; it be- comes, as I have before said, a matter of vital PNEUMATOLOGY IN THE EYE. 35 moment to my case that I should show, cri- tically, what was the SPIRIT in which his Critique on the Rationale was conducted. And first, It is manifest that, our respective Schemes of the Mind are, to the last degree, opposite and incompatible. If, therefore, his procedure with regard to me, or my views, has been unjust, or illiberal; I presume, there can be no doubt what has been the cause of his returning a profess and sincere compliment to his pretensions, by an exterminating condemnation of my labors. And here, I have to adduce what I suppose will decisively shew whether he has not followed my transgression beyond his Critique, into his Natural Magic. Jn speaking of Impressions on the Retina, in his Work in question; he breaks forth into the folio wing very extraordinary, and equally uncalled for, effu- sion : " Here we reach the gulph which human " intelligence cannot pass. And if the presump- " tuous mind of man shall dare to extend its spe- " culations farther, it will do so only to evince its " own incapacity, and mortify its pride." Now, unhappily for the philosophical tact of the Moraliser, who has thus expressed his indig- nation against intruders of this cast ; it is to be ob- served that Sir Isaac Newton had so " DARED." But, to pass over this slip of his memory ; it is here to be remarked that, Sir David Brewster's Natural Magic is written, not in a morose, or ascetic vein ; but, on the contrary, generally speaking, in a facetious, or humorous style, 36 SIR DAVID BREWSTER'S rather exciting the risibility of a reader. We are, therefore, here urged to ask : What could have STUNG Sir David Brewster into the more than stern denunciation which he has pronounced against the " BARING" of any one, who had pried into any secret of nature beyond what he himself had done ? Can it, then, be doubted Whether, or not, I am the intruding meddler at whom this denuncia- tion is pointed ? And, Can there be a moment's doubt, but it was the offence of my starting Cere- bral Vision, in the face of Pneumatology in the Eye that roused up, in his Critique, the whole assault on my optical labors, and on my whole philosophical existence; and, that broke out again in his Natural Magic ? When Sir David Brewster deemed it decorous to put on the Moralist for my amendment; as, it will presently appear, he has done in the most in- tolerable extent ; he would have done well to re- member that he was inflicting this upon a far older man than himself ; whose improvement, therefore, was utterly out of the question, and the inflicting of insult upon whom is the only discoverable motive. But, as to his warning me against the c ' DARING" of a prying into the Arcana of Nature ; or, rather, his general denunciation against all such prying; Every one who possesses the least tincture of Philosophy must SMILE at the thing ; as it must be self evident that, either the Great Architect of Nature approves of our attempts to solve the whole problem of Nature's ways ; or, else, every such attempt, the first no less than the last, must be PNEUMATOLOGY IN THE EYE. 37. impious. I confess, therefore, that I am obliged to Sir David Brewster for the lesson. It embodies a whole volume, in itself ; which nobody can mistake. It must be, for various reasons, my wish that I could, compatibly at all with my reputation, or very existence, either as a philosopher* or a man, permit the moral procedure of my Critic to close here, with what is already stated. But, it is cer- tain that my annihilation, in both capacities, has been, during seven years, consummated, for the time, by a proceeding of Sir David Brewster in his Critique, which I must now place in the view of those whom it may concern. The matter, which thus urges for statement, is the fact that, after he had finished his Critique ; wherein, he has stamped upon my labors the express charac- ter of "FOLLY :" And having, to my unutter- able surprise, proclaimed me in the face of NEWTON; whose views it has been my solace to think I have realised : Each of these denunciations being, in it- self, sufficient to warn off all men from my labors : He then pulls off the Critic's Gown ; and, vesting himself with the Monitorial Cap of the Judge, who is about to exhort a culprit previously to passing sentence upon him ; he pronounces, for my future benefit, the following advice. " We regret very much that we are obliged to " give so unfavourable an account of Mr. Team's " optical labors. If he will only leave the fields " of speculation; and, with some feelings of respect "for the researches of his predecessors, will de- " vote himself to the hard labor of experiment and 38 SIR DAVID BREWSTER'S " observation,' we have no doubt that he will do 66 something which will gain him credit, and repu- tation." When men are surcharged with a purpose; their eagerness is apt to blind their circumspection. After Sir David Brewster had thus recommended, to a man whom he knew was old, a course of ex- periment, and observation ; which advice implies the imputation that he never had experimented, or observed ; What reason could this Monitor have for " NOT DOUBTING" that such a man " might do something to gain himself credit, and reputation." What reason could he have, for "not doubting" that a "Philosopher of Folly'" might do something creditable ? The Gentlemen, to whom 1 make this Appeal, are not votaries of Fortune; but, are votaries of Knowledge. And if, in any station of life, the dignity of our nature ought to be uppermost in our esteem ; it ought, surely, to be in the Philosopher. Either Sir David Brewster believed that I was the being whom he depicted in his moral advice ; or, he did not. But, if he did believe it; then, Whence came his confident belief, his " no doubt" belief, that I could mend ? To the Gentlemen ap- pealed to, I therefore here address this case; and ask: Isthe complexion, of the monition in question, con- sistent with the dignity of their Order ? Here, at any rate, I have to represent that the individual, for whose amendment this advice was given, was at that time an old man, approaching to, and now arrived at, the unimprovable age of "three-score and ten years*" Arid, was one who PNEUMATOLOGY IN THE EYE. 39 had done his work, to the amount of a Dozen Volumes on a variety of abstruse subjects ; and which are not without their witnesses, a fact suf- ficiently known to my chastiser. The mention of these labors I have been goaded into, in order to shew what has been the literary course of the man upon whom Sir David Brewster has deemed it both just, and decorous, to inflict measureless contumely. And now, Gentlemen, it is for you, and for all honorable minds, to ASSIGN THE AMOUNT OF PHILANTHROPIC SPIRIT, which Could enable a man, dignified as my Critic is in the Phi- losophical Community, to inflict such a scathing upon the waning remains of former capabilities, in the person of one who could thus refer to his vouchers. And, here, I ask: Would this Critic have dealt out the same outrage of all feeling, to any Member Elect of the Scientific Community ? And, if he would not; then, What excuse can there be for treating any one, who had exhausted a life in the service of Science, as being out of the pale of required observances. GENTLEMEN ! The statement, now given, has far other motives, and utility, than that of relating a personal wrong. As regards myself; it, has, in- deed, the cause of an individual for its object. But it bears upon Philosophy, in the case of Vision in the Brain, with vital moment; inasmuch as it is the KEY, the only possible Key, which could en- able you to unlock the reason of Sir David Brew- ster's hostility against the discoverer of Vision in the 40 SIR DAVID BREWSTER'S Brain. It is this key which alone, moreover, could possibly enable you to unlock some of the astonishing absurdities that, I think, will appear in the Critique which has been uttered upon my Rationale : And, if possible, the still more astonishing avoidance, first and last, of the Fourth Mode or Half-field Vision; except, only, in that instance in which he names it for the depart- ment in which he proposes to refute the whole of Cerebral Vision; and, then, never adverts to it again. This part of his proceeding, indeed, is so wonderful, that it is indispensable to state the fact here ; especially, as it amounts to no less than a formal recognition of Vision in the Brain on the part of my Critic: Of which fact, I shall make due use, in its proper place. The thing is expres- sed in the Critique, in the following terms: "As the views of our Author on these sub- I f jects, are all original, and stand in direct oppo- " sitiontothe opinionsof the most distinguished phi- " losopher, and metaphysicians ; it would require a " volume as long as his own to make our readers ac- " quainted with them; and, another volume of equal " length to examine them in detail. Mr. Fearnwill, " therefore, we hope, be satisfied with an exami- II nation of his Fourth Mode of Vision; which he cha- " racterises ' as a clear field of unoccupied ground, " there not being the least evidence of its ever hav- " ing been noticed, and far less discussed, in any " extent Treatise on Optics that has fallen in my tl my way/ ' Now, as the last words, in the passage just PNEUMATOLOGY IN THE EYE. 41 given, are quoted from the Rationale: And there is much more in the Rationale on the same topic, describing the non-recognition, by all Writers,of the fact of the Fourth Mode ; It is here most urgent to ask; Whether it is not extraordinary that Sir David Brewster does not make any question of the reality of the Fourth Mode : but, on the contrary, proposes to proceed upon my assertion of 'it 1 It is needless to remark that, he would not choose a Mode of Vision, for the purpose of tryingupon it his test of Visible direction, if he did not believe in the reality of the Mode which he so chose. In a word ; I shall turn to this matter again, in the sequel: And, shall here only observe that, it forms a ple- nary virtual recognition of Vision in the Brain ; Although, certainly, he did not so intend it. If Sir David Brewster can make his own view of the subject good; it is his affair to do so. But, I suppose it is impossible to deny that he has evin- ced a confusion in his conception of the subject, in thus confounding the Fourth Mode of Vision, with Another Mode differing infinitely from it in in effects, and consequences, a mistake of such magnitude as ought to render him cautious how he deals, with unsparing severity, with any labors of others. His certain optical repute ought to be a guarantee for his infallibility. And, yet after seven years' deliberation, I would not withdraw any one position which he has condemned in my views of the subject. And, if this does not prove a very extraordinary BIAS in him ; it certainly establishes a rare amount of stupidity in me. 42 COLOR AND LIGHT THE FACT, THAT Color and Light are Two Most Different and Heterogeneous Entities. ORIGIN OF THE LAWS OF PRIMARY VlSION. After explaining, as lias been done in the fore- going Section, Sir David Brewster's project of Pneumatology in the Eye, is the proper place, in this Appeal, to entertain the fact that Light and Color are among the two most Heterogeneous En- tities which the human mind can conceive ! The Agent we call LIGHT, as far as we yet understand its nature, belongs to the category of Substance; and, it appears to be some modification of External Body. At any rate, Light operates mechanically, by motion, and by what is called contact or impulse. The other Entity in question, namely, COLOR is not a Substance; but, is a Modification or State of a Mind. Fortunately, there is not a fact in philosophy concerning which there is a more universal con- sent, than that now under consideration : Because, Color, as an affection of a mind, is one of the Bases, or Fundamental Positions, upon which any true Physiology of the Mind can be built. The Thing, thus considered is, alike, the Starting Postin the Pneumatology of Locke and of Newton, in the old school; and of Reid, and of Stewart, in that which followed and was opposed to it. Nor is this unanimity at all affected by the salvo which the Instinctive Theory of Reid led him to set up, in his assertion that Color is an external quality, name- HETEROGENEOUS ENTITIES. 43 ly, a sort of skin attached to the outsides of bodies, as the Vulgar take it to 4 be : And, that we have in the mind a sensation, which Dr. Reid calls " the Appearance of Color." Criticism would be disgraced by any words employed with intent to render this salvo worthy of philosophical consideration. And, accordingly, in the writings of Professor Stewart, we have ample expressions to evince his dissatisfaction, and complete dissent, from this device of his Teacher. Nothing, indeed, can be more certain than the total SPLIT TO THE BOTTOM between the fundamental views of those two otherwise-united philosophers : Although, Professor Stewart appears to have made it a point of chivalry, to carry his Teacher upon his shoulders, through all the perils, and all the ultimate wreck, of the Instinctive Theory. The controversy between Mr. Stewart and my- self, regarding who was the original proposer of the fact of a a Variety of Colors being necessary to our perception of Visible Outline : He having, in his "DISSERTATION" prefixed to the Encyclo- paedia Britannica, in the year 1818, asserted that, "he had differed from Dr. Reid more ihanf or ty years ago," on the subject: Whereas, I had published my " Demonstration of the Laws of Primary Vision" in the year 1814. And having, in his Dissertation, affirmed that nothing can be more self-evident than that a variety of Colors is necessary to the act of perception in question : Both these proceedings prove, inevitably, that there was a SPLIT ; and, this split no higher up than at the very foundation of 44 COLOR AND LIGHT their Theory. At the same time, it seems won- derful that we find not so much as a hint of this difference, in all the Five succeeding Editions of Mr. Stewart's Elements. And the matter comes out only in the " Dissertation, " some years after I had started my Theory of Perception by a discrimi- nation between any Two contrasting Sensations of Colors, as discerned by the Intellect. My having written to Mr. Stewart, asserting my claim to the Originality of the thing, has nothing to do with the present purpose: Although it has been accorded to me by a number of Periodical Writers ; and, denied by not one. But, certainly, the whole matter sets the Instinctive Theory for ever at rest. And here, the grinding evil of unexampled pres- sure urges me to appeal the following question, to all genuine minds : After Professor Stewart had suffered the schism in question, between himself and his Teacher, to remain buried from the public "more than forty years": Is there then any ap- pearance that he would, after those forty years, have awakened the public attention to the matter, if he had not deemed himself obliged to do so by the forthcoming of my Laws of Primary Vision ? This question cannot, for a moment, admit of an answer in the affirmative. Mr. Stewart's only mention at all, of the very important fact, is dated about four years after the date of the Laws of Vision . And this bore upon my pretensions to their originality, so as to bring on my remonstrance to Mr. Stewart. There cannot, then, exist a doubt, but mv humble labor roused Professor Stewart to HETEROGENEOUS ENTITIES. 45 assert that he had been long in the possession of the generic fact; though, not in that of the ANA- LYSIS. For my own part ; I have not a doubt of Mr. Stewart's ingenuousness, in his claim to the gener- ic fact. But, his knowledge of it was such as was not available, or not availed of by him. And, now, I ask, Where has been the liberality, or the justice, of my Country ; in that I have pined on, these twenty five years, since the Laws of Vision gave the Reideiam Theory to the winds ? Here it is to be duly understood, that Mr. Stew- art, on my call upon him, did not arrogate to himself the originality of the generic fact of the Laws of Vision : But, only alleged that, he had met with the thing "in several authors before he had ever heard of my name." One of these Writers he has quoted, as his authority, namely Lord Monboddo. And we must suppose that he had not a more effective authority to quote. Now I have, in my Prefix Letter to Mr. Stewart in my "First Lines of the Mind," stated the extent of Lord Monboddo's pretensions. And, the Monthly Review for Feb. 1822 has afforded a most pointed and decisive commentary, on Mr. Stewart's appeal to Lord Monboddo. But, three, or four, such effective appeals to the Country, as that in the Monthly Review, have availed nothing to the subject. But, to resume the subject of the Misnomer, and Misconception, in question. There has ob- tained, among Optical Writers, a custom of employ- 46 COLOR AND LIGHT ing the two Terms in question,, namely LIGHT and COLOR as synonymous terms. And, along with this has been included an error in men's con- ception of the two Notions which those names signify. Now the cause of the misnomer is per- fectly obvious. And, when we are reasoning in the Science of Lucernal Optics, the misnomer is at once both convenient and harmless ; especially convenient, because it saves much circumlocution, or verbiage, in a demonstration. But, when the misnomer is attempted to be introduced into the Science of Mind:, the most disastrous results must necessarily follow. It is, indeed, unnecessary to enlarge upon a truth that must be manifest, on its mere proposal, to every person in the subject of Mind. Accordingly, it fully appears that Sir Isaac Newton had a serious boding that some mischief would, at some time, arise from the pervertion of the two Names, to signify one same Nature. And although, for the sake of its convenience in Exter- nal Optics, he gave into the usual phraseology ; he he has entered his protest against the usage, in order that it should never be carried into Pneu- matology. Under the name of a DEFINITION of Light, in his Optics, Newton says; " The homogenial light " and rays which appear or rather make objects " appear so, I call rubriffic or red making; and " those which make objects appear yellow, green, " &c. I call yellow-making, green-making ; and so " on of the rest. And, if at times I speak of light HETEROGENEOUS ENTITIES. 47 " or rays as coloured, or endowed with colour, " I would be understood to speak not philosophi- " cally and properly, but grossly, and according " to the conceptions of vulgar people. For in them " is nothing more than a certain power, and " disposition, to stir up a sensation of this, or that, " Colour." One would think it would be impossible to hang out a more signal banner, in order to warn off all men from breaking down the partition between Color and Light. In the face of this warning, however, we find Sir David Brewster trampling upon the distinc- tion between Light and Color : And viewing the two most Heterogeneous Entities of human concep- tion AS ONE ENTITY! Thus, he not only makes the Retinal Impressions travel, like Railroad Wag- gons, up and down the Optic trunks : Which, indeed, I affirm they actually do backwards : (And, as Automatic Reactions, they may travel forwards from the Mind to the Eye in the case of the mind's suffering either Memory, or Imagination, or Reverie ;) But, besides this, he makes our Sensations of Colors travel, along with the retinal impressions. And, in this, he pro- ceeds as the merest novice in the Philosophy of the Mind would not follow him. As for the nature of the retinal impressions ; I do not see that we can refuse the opinion of Sir Isaac Newton, that the Rays of Light prick the retina with their points. And, the different rays being of different densities, occasion deeper, or 48 COLOR AND LIGHT lighter impulses on the retina ; and these different degrees of impulse occasion correspondent sensa- tions of color. Now, if this be entertained ; I will propose an analogy of the subject. The prick- ed Retinal Impressions are analogies to window frames. And these window frames travel empty up the Optic Trunk, until they reach the Percipient Mind. In this case, the Mind sup- plies Pictures in Colors, which exactly fit the frames. But, the frames remain on the outside of the mind; while, the pictures preserve their distinctive features or demarcations, and thus form a whole landscape, or a resemblance of any external object that occasions the vision in question. This analogy is no other, in kind, than Mr. Locke's Pictures in a dark room. The only thing in which he was defective, in this case, is that he did not reduce his Scheme to any analy- tical demonstration, as he certainly did not know the fact that visible lines are the Interlimitations of our Sensation of Colors. If either he, or Bishop Berkeley, had known this ; he must have known that Visible Lines are breadthless, a fact which neither of these, nor any other writer, ever so much as suspected. But Locke was right in gross: al- though, not analytically definitive. And, in fact, all Philosophers, both Ancient and Modern, have thought like him; with more, or less, of indistinct- ness in their conceptions of the Figured Objects which Sight reveals to us. 49 SIR DAVID BREWSTER'S PRETENDED REFUTATION OF RECROSS CEREBRAL VISION by the Alleged Principle of the Visible External Direction of Objects from the Eye. In entering upon the discussion of the present head, I have in the outset to observe that the Sub- ject itself is in the highest degree important in its bearing upon Mental Philosophy ; and, especially, upon the Problem of the Physical Intercourse which is carried on between the Percipient Mind and the External Cause of its Sensations, which is no other than the Various Modifications of the Agent which we call Body : a Subject which, if it has been substantiated up to the point of a suffi- cient recognition ought, certainly, to effect a resus- sitation of the worse than sleeping interest of our Countrymen, by rousing their attention to a New Epoch in the Science of Pneumatology ; and, to the opening of new prospects, and hopes, of the Destiny of our Species, in an indication of future states of existence, and of mental development. With a view, then, to the description of the sub- ject now contemplated, I observe in the outset that I shall, for the moment, lay aside every consideration of the inconsistency of Sir David Brewster's at- tempting to refute Cerebral Vision by the Principle of Visible Direction, when he himself had explod- ed that Principle by the proposal of Pneumatology in the Eye. The incompatibility of the two doc- 50 SIR DAVID BREWSTER'S trines in question is so striking that, one is totally at a loss to conjecture how it would have escaped the notice of my Critic. But, the business of Philosophy, here, is with the FACT of the case ; and, is not so immediately with the consistency of those who attempt to treat the fact. To commence, then, with the statement of Sir David Brewster, in this case : He has selected my "Fourteenth Proposition" for the subject of refutation. And, to this choice I offer no objec- tion : although, it presents a case of vision from an external object ; whereas, any such case is much less safe from the chances of mistakes, than a case in which no external object is the occasioning cause. Next : I have to accord to my Critic, that he has quoted the long title of my Fourteenth Propo- sition, including all its variety of italics, and SMALL CAPITALS, with great precision. But, it is to be observed that, at the time he was writing the Cri- tique, he had not yet broke out into rebellion against the Principle of Visible Direction ; because it appears, from dates, that it was about a year after his writing the Critique, that he published his Pneumatology in the Eye, in his Natural Magic. Judging from the general tone of his strictures, therefore, we may conjecture that his punctilious exactness, with regard to my verbiage in the title, arose from his being elated with the thought of annihilating the whole of Cerebral Vision at a single blow. And, indeed, he expressly boasts of having indulged my letter-press : And thus evinces PRETENDED REFUTATION. 51 a triumphant feeling, in the thought of vanquish ing an opponent. And here a consideration occurs, which at least claims to be mentioned. I might naturally have been led to think that, no cause could give rise to the amount of exterminating censure which has been heaped upon me as author of the Rationale, except such an event as my bringing forth that Treatise in the face of Sir David Brewster's Pneu- matoloyy in the Eye. But there is certainly another imaginable cause, which might produce a very considerable degree of hostility. And this must here be taken into the calculation. It is manifest that Sir David Brewster's desire of Optical Fame is immeasurable, a laudable desire if maintained within the limits of justice to others ; but which, otherwise, may produce a great amount of mischief both to individual right, and to science. Now, the question here is, Whether philosophical jea- lousy, by itself alone, has brought upon my labor and myself, all the scathing which both have under- gone at the hands of my Critic ? If this be sup- posed ; it will follow that Sir David Brewster had not broke out into revolt against the Principle of Visible Direction when he attempted by its efficacy to overthrow Cerebral Vision. It is obvious that, in the case of any one possess- ing an inordinate ambition to engross the whole Science of Optics; it must be a strong pull against that ambition to have the Science of Cerebral Vision snatched for ever, from his grasp. Whether, or not, this has been the cause of Sir David Brew- E3 52 SIR DAVID BREWSTER'S ster's unqualified hostility to me, I leave it to others to judge. But, at any rate, the TENOR OF HIS CRITIQUE stands a monument of his feeling : Which feeling can admit of no palliation from any intended act of mine. But, to resume now the statement of Sir David Brewster. He has quoted my Fourteenth Proposi- tion as follows : lf fact . THE IMAGES CHANGE SIDES IN THE BRAIN 4f 'DUPLICATED NOSE t TWO #GROS