( 136 ). 



V. — On a Mode of Vieiving the Seconds Hand of a Watch 

 through a Beetles Eye. By Dr. Whittell. 



In one of the earlier mimbers of the ' M. M. Journal' a writer 

 described some interesting results produced by experiments on a 

 beetle's eye as seen under the microscope. Amongst other facts he 

 mentioned that the movement of the seconds' hand of a watch could 

 be made visible through each of the numerous lenses of which the 

 eye is compounded, but as he had only read of the experiment, 

 he was unable to explain the mode of procedure. In looking about 

 for something interesting to exhibit at the late soiree of the 

 Adelaide Club, 1 made many experiments with a view to produce 

 the above-named result, and after numerous failures I hit upon the 

 following simple but effective plan, which I venture to submit, 

 with the hope that it may be of some use to the readers of the 

 Journal. 



Take a watch with a white face, take out the front glass, and 

 remove the hour and minute hands. Paste over the face of the 

 watch a piece of dead-black paper with a round window cut in it, 

 80 as to leave nothing exposed but the small circle in which the 

 seconds' hand rotates. Place the watch on the front of the mirror 

 of the microscope, and condense the light of a strong flame on the 

 small white circle that has been left exposed. Keflect this light 

 through the beetle's eye, previously placed on the stage, just in the 

 same manner as if the ordinary mirror were being employed. 

 Bring the eye into focus, and then gradually draw back the objec- 

 tive by means of the fine adjustment until the images of the watch 

 hand appear. At first these will probably be dim, but by varying 

 the inclination of the watch and careful adjustment of the light 

 the observer will at length obtain a bright and distinct image 

 through each lens of the eye. The nearer the watch can be brought 

 to the stage without cutting ofi" light from the condenser, the larger 

 will be the image. Any power may be used from i to ^ inch, but 

 I prefer a y\th, with a No. 2 eye-piece. Under this power the 

 images are sufficiently enlarged, and a good number of them are 

 included in the field. The eye may be mounted in balsam, but I 

 think I have obtained better results from one specially prepared 

 and mounted in glycerine. 



Adelaide, South Australia. 



