780 Dr. Francis Ward [June 6, 



WEEKLY EVENING MEETING, 

 Friday, June 6, 1913. 



His Gkace The Duke of Northumberland, P.O. K.G. D.C.L. 

 LL.D. F.E.S., President, in the Chair. 



Francis Ward, Esq., M.D. Edin. M.B. CM. 



Reflection as a Concealing and Revealing Factor in Aquatic 

 and Sub-Aquatic Life. 



[abstract.] 



As a result of observations and experiments carried out on ponds 

 built for the purpose, and by the use of apparatus for observing 

 organisms in their natural environments, I have arrived at certain 

 conchisions as to the value of reflection as a concealing factor in 

 various forms of aquatic and subaquatic life. The general principle 

 upon which these ponds are built is as follows : In one bank of the 

 pond is a glass window, and beyond this window an underground 

 observation chamber. No light enters this chamber except through 

 the surface of the water By this means everything in the pond is 

 seen by entirely natural illumination, the observer cannot be detected, 

 and as there is no reflection from the glass the making of photo- 

 graphic records is greatly simplified. In the first pond, built for 

 the observation of objects in the water, the glass is perpendicular. 

 In the second, for observing objects on the surface, the glass is at an 

 angle of 45° to the surface. 



The apparatus I use consists of a tube 18 inches square and 5 feet 

 long, on one side at the lower end is a window ; a reflex camera 

 slides into this tube, so that the lens is opposite the glass. When 

 in use, a heavy weight carrying a hook is lowered into the water, 

 with the end of the tube attached to the hook. The whole apparatus 

 can be tilted at any angle, and by this means the incident rays 

 from any object in any position— except overhead— are made to strike 

 the glass at right angles, and thus distortion, due to refraction 

 through the glass, is rendered negligible. 



The apparatus has been mainly used as a check upon observations 

 in the ponds. 



For observing and photographing life on the bottom, I use a 

 tube 3 feet long, with a glass partition inside, a foot from the end. 

 This apparatus acts as a boat-like sea telescope, and is fitted with a 

 camera. Lastly, through the kindness of Professor Herdman, I 



