254 Fortieth Annual Meeting 



that light reflected from intervening surfaces which would 

 fog the image on the plate if the camera was focused on 

 an object beneath the surface of the water. It may be 

 explained at this point that the attempts to photograph sub- 

 merged bodies in the ordinary manner, with the lens ex- 

 posed, have usually resulted in failure because the exposure 

 is made through the surface contact of two media, water 

 and air, of very different refractive power. If the surface 

 of the water is not perfectly smooth, as it is through the 

 aquarium side or through the glass in the bottom of the 

 water-box, the curving, rippling, irregular surface acts as 

 a myriad of convex and concave mirrors that magnify, or 

 reduce, or diffuse the image on the plate. Even when the 

 surface of the water is perfectly smooth, unless precautions 

 are taken to cut off the direct light as shown in the arrange- 

 ment of the camera and the windows, the rays of light that 

 come from the object beneath the water enter the camera 

 at the same time with those that come from the glass side 

 of the aquarium, or the reflecting surface of the water, in 

 a way to destroy the clearness of the image. 



The use of this apparatus was necessarily limited and its 

 object largely experimental. It is difficult to work on the 

 edge of the coral reef with such a clumsy apparatus, as the 

 waves break over them, even on a calm day. But the 

 trouble caused by the turbidity of the water, resulting from 

 the stirring up of the sand as the operator moved about, or 

 the waving motion of the marine plants as currents of water 

 pass through them, is little short of maddening. Add to all 

 the foregoing sources of annoyance the difficulty of bal- 

 ancing yourself, keeping the black cloth over your head, 

 steadying the instrument against the movement of the 

 water while focusing the camera, keeping the water-box 

 glass dry and making the exposure, and you will have in 

 mind a few of the multitude of little things that cause many 

 failures, before even a recognizable picture can be secured 

 of the life on the edge of a coral reef. I am free to confess 

 that while I secured several plates that were fair, consider- 



