Nature . gauze, the one containing 75 meshes to the linear inch,the other 50 ; a slit .^^ inch (i mm.) in width was placedbefore the lens. An attempt was made to count the greatest number ofimages that could be seen with fair distinctness. Thewhole of the filament was screened from view except ashort portion of one limb, which was viewed from adistance of about 8 feet through a horizontal slit and alens of 5 inches focus. According to the estimates ot. several different observers, the number of images wasgreater than :o and less than 30 (whence it is calculatedthat without the slit there would
Nature . gauze, the one containing 75 meshes to the linear inch,the other 50 ; a slit .^^ inch (i mm.) in width was placedbefore the lens. An attempt was made to count the greatest number ofimages that could be seen with fair distinctness. Thewhole of the filament was screened from view except ashort portion of one limb, which was viewed from adistance of about 8 feet through a horizontal slit and alens of 5 inches focus. According to the estimates ot. several different observers, the number of images wasgreater than :o and less than 30 (whence it is calculatedthat without the slit there would be some 50o\ Exactenumeration is perhaps impossible, for though at thefirst glance one receives the impression that the numberis quite definite and probably about 25, closer examin-ation shows that it is often very difl^icult to localise theline of demarcation between successive images. If the distance between the eye and the incandescentfilament is much more than 8 feet, or if a lens of shorter April 13, 1899] NA TURE 561 focus is employed, the multiple images become blurredand indistinct. The appearance ultimately presented isthat of a band of light crossed by a very large number—probably 400 or 500—of hazy dark lines at right anglesto its length. These might be produced by somestructure in or near the crystalline lens or the corneacomposed of elements measuring about tjoW ^^ length or breadth. I do not know of any simple structure suffi
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