A New System for Preventing Collisions at Sea 



covered that certain kinds of bats had a veritable sixth sense ; 

 he noticed that the particular kind that possessed this re- 

 markable sense was only provided with extremely small eyes 

 that could be of little or no use to them in the dark still 

 they found their way about quite as well as cats and owls 

 which have very large eyes. He then made experiments by 

 blotting out the eyes of bats with red-hot irons and found 

 that they got along just as well without eyes as with them. 

 I quote the following from Cassell's Natural History : 



" He blinded these animals, sometimes by burning the eyes 

 with a red-hot wire sometimes by removing the organs altogether, 

 and even filling up the orbits with wax, and then allowed them 

 to fly. In spite of the mutilation, the unfortunate little creatures 

 continued quite lively, and flew about as well as those which still 

 retained their eyes ; they did not strike against the walls of the 

 room, or the objects in it, avoided a stick held up before them, and 

 showed a greater desire to keep out of the way of a cat or the 

 hand of a man than to escape contact with inanimate objects. One 

 of these blinded bats was set free in a long underground passage, 

 which turned at right angles about its middle. It flew through 

 the two branches of this passage, and turned without approaching 

 the side walls. During its flight it detected a small cavity in the 

 roof at a distance of eighteen inches, and immediately changed 

 its course in order to conceal itself in this retreat. In a garden 

 a sort of cage was prepared, with nets, and from its top sixteen 

 strings were allowed to hang down. Two bats were introduced into 

 this enclosure, one blinded, the other with its eyes perfect. Both 

 flew about freely, never touching the strings with more than the 

 tips of the wings. Finally, the blind bat discovered that the meshes 

 of the enclosing net were large enough for it to get through, and 

 made its escape ; and after flying about for a time, made its way 

 rapidly and directly to the only roof in the neighbourhood, in which 

 it disappeared. In a room containing numerous branches of trees, or 

 in which silk threads, stretched by small weights, were suspended 

 from the ceiling, the bats, though blinded, avoided all these 

 obstacles ; and when, after tiring themselves with their aerial evolu- 



