On the Formation of Multiple Images in the Normal Eye. 243 



of nearly circular outline. If the light was made stronger, each of the 

 circumferential discs acquired a pointed tail, directed radially outwards, 

 and the whole appeared like a six-rayed star. So far there is little or 

 nothing new in the observation. 



The observer then gradually moved backwards, still holding the lens 

 at his eye ; the outer discs at once began to elongate radially, and each 

 soon became resolved into two or more, the approximate symmetry of 

 the figure being still retained. When the distance from the eye to the 

 hole was 3 feet, the number of images that could be counted was about 

 twenty, and the appearance presented was happily likened, by an expert 

 person who confirmed my observations, to that of a large unripe black- 

 berry. If an orange-yellow glass were substituted for the dark red 

 one, the stronger illumination again gave rise to the development of 

 tails, and the blackberry became transformed into a beautiful flower. 

 At 4 feet distance the images had increased to about forty, which was 

 nearly the greatest number that could be counted with any degree of 

 certainty. But, while becoming much less easily distinguishable, they 

 still obviously continued to multiply. At 25 feet there was seen a 

 mottled luminous patch streaked with a few bright lines, evidently cor- 

 responding with the sutures of the crystalline lens. These bright lines 

 were found to consist of overlapping images of the round hole, and 

 traces of many similar images could be detected in different parts of the 

 mottled patch. 



The above described effects can be observed equally well and with 

 but little modification when the lens employed is convex instead of 

 concave ; indeed, any one who is skilled in the mangement of his eyes 

 may dispense with the lens altogether. 



I have tried to describe the phenomena as seen with my left eye. 

 With the right eye they are of the same general character, but differ in 

 details ; in particular, the separate images first seen are less symmetri- 

 cally arranged, and their number appears to be eight instead of seven. 

 The observations in question would be found difficult or impossible by 

 a novice in optical experiment, partly on account of his inability to 

 keep his eye in a definite state of accommodation, but chiefly perhaps 

 because he would not recognise what he saw. 



I thought that the observations might be rendered easier if the 

 source of light had a more distinctive and conspicuous form than that 

 of a simple circle. Experiments were, therefore, made with a semi- 

 circular hole, and this was in some respects an improvement ; but far 

 better results were afterwards obtained by using as a source of light 

 the horseshoe-shaped filament of an electric lamp, screened by a coloured 

 glass. When such a lamp was looked at through a lens, concave or 

 convex, of about 6 inches focal length, from a distance of a few feet, 

 the roughly oval patch of luminosity formed upon the retina appeared 

 to be made up of a crowd of separate images of the filament, some 



