,illustration3 ,i ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,,spectropia2 ,,or1 ,,surprising ,,spectral ,,illusions4 ,,showing ,,ghosts ,,everywhere1 ,,and ,,of ,,any ,,colour4 ,,by ,j4 ,h4 ,,brown4 ,,fourth ,,edition4 ,first ,series4 ,,with ,,sixteen ,,illustrations4 ,,london3 ,,griffith ,,and ,,farran1 ,,successors ,,to ,,newbery ,,and ,,harris1 ,,corner ,,of ,,st4 ,,paul',s ,,churchyard4 ,h4 ,c4 ,,treacher1 ,,brighton4 ,,mdccclxv4 ,entered at ,stationers' ,hall4 ,,introduction4 ,the following ,illusions are founded on two well-known facts2 namely1 the persistency of impressions1 and the production of complementary colours1 on the retina4 ,the explanations are divided into two ,parts4 ,the ,,first consists of directions for seeing the spectres4 ,the ,,second1 a brief and popular1 as well as a scientific1 description of the manner in which the spectres are produced1 and is intended for the use of those who may wish to know more of this subject than is contained in the first ,part4 ,as an apology for the apparent disregard of taste and fine art in the plates1 such figures are selected as best serve the purpose for which they are intended4 ,j4 ,h4 ,,brown4 ,,old ,,steyne1 ,,brighton4 ,,directions4 ,to see the spectres1 it is only necessary to look steadily at the dot1 or asterisk1 which is to be found on each of the plates1 for about a quarter of a minute1 or while counting about twenty1 the plate being well illuminated by either artificial or day light4 ,then turning the eyes to the ceiling1 the wall1 the sky1 or better still to a white sheet hung on the wall of a darkened room 7not totally dark71 and looking rather steadily at any one point1 the spectre will soon begin to make its appearance1 increasing in intensity1 and then gradually vanishing1 to reappear and again vanish2 it will continue to do so several times in succession1 each reappearance being fainter than the one preceding4 ,winking the eyes1 or passing a finger rapidly to and fro before them1 will frequently hasten the appearance of the spectre1 especially if the plate has been strongly illuminated4 ,those who use gaslight will find it convenient1 after having looked at the plate as above described1 to extemporise a darkened room by having the gaslight turned low2 or one end of the room may be darkened by placing a screen before the gas1 lamp1 or candle light4 ,the spectres may be easily made to appear life-sized or colossal1 by having the plate nearer the eyes while receiving the impression1 and by increasing the distance between the observer and the surface against which they are seen4 ,as a general rule1 the observer should be about eight to twenty feet from the surface4 ,when the spectres are seen against opposite houses1 the sky1 and other distant surfaces1 they will appear colossal4 ,should any one not be able to see the spectre's features1 the reason will be1 either that the eyes have been allowed to wander1 or the head to move1 while looking at the plate4 ,many persons will see some one coloured spectre better than the others1 in consequence of their eyes not being equally sensitive to all colours4 ,the colours in the plate will be found to reverse themselves in the spectres1 as explained elsewhere1 the spectres always appearing of the complementary colour to that of the plate from which it is obtained4 ,thus1 blue will appear orange1 and orange blue1 c4 ,,list ,,of ,,the ,,plates4 ,,plate ,i4 ,this winged figure of ,victory will give a white spectre by artificial light 7rather green by daylight71 the red wreaths green1 the green roses red1 and the orange stars blue4 ,,plate ,,ii4 ,this black figure will give a white spectre4 ,,plate ,,iii4 ,this will give a dark spectre4 ,,plate ,,iv4 ,this green figure will give a red spectre4 ,,plate ,v4 ,and this red figure will give a green spectre4 ,,plate ,,vi4 ,this orange figure will give a blue spectre4 ,,plate ,,vii4 ,and this blue figure an orange spectre4 ,,plate ,,viii4 ,this purple hand will give a yellow spectre4 ,,plate ,,ix4 ,and this yellow figure of ,victory will give a purple spectre4 ,,plate ,x4 ,the face of this figure will come out green in the spectre1 the garment red1 and the cloud white4 ,,plate ,,xi4 ,this black skeleton will make a white spectre4 ,,plate ,,xii4 ,this skeleton will also give a white spectre1 with a yellow mantle4 ,,plate ,,xiii4 ,this figure and broom will give a yellow spectre1 cloak and hat red1 and moon white4 ,,plate ,,xiv4 ,these figures will give green and yellow spectres4 ,,plate ,,xv4 ,this ,cupid will give a rose-coloured spectre1 with bow and arrow yellow4 ,,plate ,,xvi4 ,this is a rainbow with colours reversed1 the spectre of which will be found a good resemblance of nature1 especially when seen on a cloudy sky4 99 99 99 99 99 ,the colours of the spectres produced by these figures will not only be subject to a slight variation in different eyes1 but also by the degree in which the plates are illuminated while being looked at4 ,a ,,popular ,,and ,,scientific ,,description4 ,it is a curious fact that1 in this age of scientific research1 the absurd follies of spiritualism should find an increase of supporters2 but mental epidemics seem at certain seasons to affect our minds1 and one of the oldest of these moral afflictions--witchcraft--is once more prevalent in this nineteenth century1 under the contemptible forms of spirit-rapping and table-turning4 ,the modern professor of these impostures1 like his predecessors in all such disreputable arts1 is bent only on raising the contents of the pockets of the most gullible portion of humanity1 and not the spirits of the departed1 over which1 as he well knows1 notwithstanding his profane assumption1 he can have no power4 ,one thing we hope in some measure to further in the following pages1 is the extinction of the superstitious belief that apparitions are actual spirits1 by showing some of the many ways in which our senses may be deceived1 and that1 in fact1 no so-called ghost has ever appeared1 without its being referable either to mental or physiological deception1 or1 in those instances where several persons have seen a spectre at the same time1 to natural objects1 as in the case mentioned by ,dr4 ,abercrombie1 in his work on 8,the ,intellectual ,powers30--8,a whole ship's company were thrown into the utmost consternation1 by the apparition of a cook who had died a few days before4 ,he was distinctly seen walking ahead of the ship1 with a peculiar gait1 by which he was distinguished when alive1 from having one of his legs shorter than the other4 ,on steering the ship toward the object1 it was found to be a piece of floating wreck40 ,a ghost1 according to the general descriptions of those who fancy they have been favoured with a sight of one1 appears to be of a pale phosphorescent white1 or bluish white colour2 usually indistinct1 and so transparent that objects are easily seen through it4 ,when moving1 it glides in a peculiar manner1 the legs not being necessary to its locomotion4 ,all the senses are more or less subject to deception1 but the eye is pre-eminently so2 especially in the case of individuals who are in ill health1 because the sensibility of the retina is then generally much exalted1 as is also the imagination4 ,we may divide the illusions to which the sense of sight is liable into four kinds4 ,first1 mental1 or those arising in the brain itself1 and only referred to the eye4 ,second1 those produced by the structure of the eye4 ,third1 those arising from the impressions of outward objects on the retina4 ,fourth1 those produced by various combinations of the foregoing4 ,it is only the second and third we shall have occasion to touch upon4 ,but before we can well understand their nature1 it will be necessary to get a slight knowledge of the structure of the eye1 and some idea respecting the nature of light4 ,illustration3 ,,fig4 #a4 ,with perhaps the exception of the ear1 the eye is the most wonderful example of the infinite skill of the ,creator4 ,a more exquisite piece of mechanism it is impossible for the human mind to conceive4 ,the annexed diagram 7,fig4 #a7 of a horizontal section of this organ will give a better idea of its general structure than whole pages of letter-press4 ,it will be seen to consist of a globe of three envelopes or coats1 which are kept distended by three transparent humours or lenses3 the aqueous 7e71 the crystalline 7f71 and the vitreous 7g74 ,the outer coat 7a7 is dense1 white1 and fibrous4 ,in front of the eye it gives place to a perfectly transparent one1 called the cornea 7d74 ,the next coat1 the choroid 7b71 is vascular1 very black on its internal surface1 in order that light falling on it through the pupil 7h7 may not be reflected4 ,the pupil is an opening through a diaphragm which is called the iris 7i71 from its colour varying in different individuals4 ,it has the power of expanding and contracting the pupil1 for the purpose of regulating the supply of light to the retina 7c71 or third and last coat which lies immediately on the choroid4 ,it is transparent1 very complex1 and the only part of the eye we shall carefully consider4 ,the following diagram 7,fig4 #b7 represents a section of it magnified #bej diameters1 a is called the limitary membrane1 and forms its innermost surface1 or that which is next the vitreous humour2 b consists of the layer of optic nerve fibers2 c is a layer of grey nerve cells2 d1 two layers in which the principal retinal blood-vessels are spread out2 e1 two layers of granular matter2 f1 ,jacob's membrane1 or layer of rods and cones4 ,fig4 #c will give some idea of the supposed connexion between these various parts1 the same letters referring to the same parts as in ,fig4 #b4 ,illustration3 ,,fig4 #b4 ,illustration3 ,,fig4 #c4 ,when a ray of light enters the eye1 it passes through the humours or lenses1 and is formed by them into an image1 on the choroid1 of the object looked at4 ,the extremities of the rods and cones have the power of appreciating the image there formed1 and convey it up through the ultimate parts of the retina 7,fig4 #b71 thence along the optic nerve fibres to the brain4 ,we are inclined to regard the extremities of the rods and cones as the true seat of perception1 in consequence of observing a considerable distance between the retinal blood-vessels and the choroid1 when performing ,purkinje's experiment4,a ,this experiment consists in passing a lighted candle slowly to and fro before the eyes1 at about two or three inches from the nose1 when the retinal vessels will exhibit themselves before the observer not unlike branching trees4 ,they may be seen by daylight1 by passing the large teeth of an ordinary comb slowly backwards and forwards before the eye1 whilst looking on a smooth sheet of paper1 or upon the sky4 ,fig4 #d represents those of the left eye1 as seen by candlelight4 ,the spot marked k is the exact centre of the retina4 7,the same letter marks the same spot in ,fig4 #a47 ,it is the seat of most distinct vision4 j is the entrance of the optic nerve 7,figs4 #d and #a71 from the centre of which the retinal artery will be seen emerging and spreading over the entire retina2 but in the diagram that part only is represented which could be seen tolerably distinct4 ,the background to the artery appears of a pale red1 except at the part occupied by the optic nerve1 where it is white4 ,a ,this distance can easily be perceived by getting an impression on the retina1 according to the 8,directions10 page #d1 and then1 on performing the above experiment1 the arterial ramifications and the central spot will be distinctly perceived to move over the spectral figure4 ,illustration3 ,,fig4 #d4 ,after this rapid glance at so complicated a structure1 and bearing in mind that some persons can see its several parts with vastly greater facility than others1 it cannot be a matter of surprise that individuals not aware of these facts are1 now and then--especially at night1 and when carrying a light about--startled by what they fancy an apparition1 but which is in reality nothing more than some part of the structures above considered4 ,a lady assures us that she saw the ghost of her husband as she was going downstairs with a lighted candle in her hand4 ,the spot k1 ,fig4 #d1 when seen against a wall a few feet distant1 appears about the size of a human head1 and wants very little to furnish it with features4 ,figured paper on the wall1 and a host of other things1 may supply them1 or even the retinal artery1 which often lends body and limbs4 7,fig4 #e47 ,illustration3 ,,fig4 #e4 ,besides the above-mentioned structures1 there are others which may play an important part in these illusions1 especially the common musc volantes1 so called from their resemblance to flying flies4 ,they consist of cells and filaments1 the dbris of the structures of the eye1 and float about in its humours4 ,that some of them exist very near the retina appears evident from the fact that1 on placing the eyes close to a gauze wire blind1 distinct miniature images of parts of the gauze will be seen in them4 7,fig4 #f47 ,illustration3 ,,fig4 #f4 ,we now pass on to consider some of the leading properties of ,light4 ,there have been many theories propounded from time to time in order to explain the various phenomena connected with this subject1 but only one accords well with all1 and that is called the undulatory or vibratory theory1 which1 from its numerous complications1 will compel us to confine ourselves to a consideration of that part only which is necessary to our present use4 ,this theory regards light as the vibrations of an imponderable ether pervading all space1 the number of these vibrations varying in a given time for each of the three primary colours--blue1 yellow1 and red--the greatest number producing blue1 the least red1 and an intermediate number yellow1 all other colours being produced by the combination of these in various proportions4 ,any two of the three primary colours mixed together makes the complementary colour to the third1 and the third is also complementary to it4 ,thus1 blue and yellow make green1 which is the complementary colour to red2 red and blue make purple1 complementary to yellow2 yellow and red make orange1 complementary to blue4 ,when the three primary colours are mixed together1 white is the result3 so that when a ray of white light falls upon a piece of paper1 and all the vibrations are equally reflected1 the paper will appear white1 and if they are all absorbed1 it will appear black2 but1 if the paper absorbs some and reflects others1 it will appear coloured4 ,thus1 if it absorbs those producing red1 it will appear green1 from the mixture of the vibrations producing blue and yellow2 and if it absorbs blue and yellow1 and reflects red1 then it will appear red4 ,in this manner any object we look at will appear of any particular colour1 according to which vibrations it absorbs and which it reflects4 ,the retina is so admirably constructed that it is susceptible of different impressions of colour by these different vibrations1 except in the case of a few individuals1 who are either blind to all colour1 and therefore see everything black or white1 and their intermediate shades1 or who are blind to only one or two colours4 ,when we look steadily at a red object for a few seconds1 that part of the retina on which the image impinges begins to get less sensitive to vibrations producing red1 but more sensitive to those producing blue and yellow2 so that on turning the eye away from the red object1 and permitting a little white light to enter it1 that part of the retina which received the red image will1 in consequence of its diminished sensibility to that colour1 and its exalted sensibility to blue and yellow1 be able to perceive the two latter colours best1 and by their mixture will give rise to a green image of the red object4 ,the same thing will be observed with all the other colours2 the secondary image or spectre always appearing of the complementary colour to the object from which the impression is obtained4 ,the duration and vividness of these impressions on the retina vary greatly in different individuals1 and can be procured from almost any object4 ,a person may1 after looking steadily1 and as often happens1 unconsciously1 for a short time at printed or painted figures1 on paper1 porcelain1 c41 see1 on turning the head in some other direction1 a life-sized or colossal spectre 7the spectre appears larger the greater the distance of the surface against which it is seen71 and there can be little doubt but that many of the reputed ghosts originate in this manner4 ,illustration3 ,,ii ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,iii ,illustration3 ,,iv ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,v ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,vi ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,vii ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,viii ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,ix ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,x ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xi ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xii ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xiii ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xiv ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xv ,designed by ,j4 ,h4 ,brown1 ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4 ,illustration3 ,,xvi ,designed by ,j4 ,h4 ,brown1 and ,published ,dec4 #ai4 #ahfc1 by ,griffith ,farran1 ,s4 ,paul's ,church ,yard1 ,london4