PBOCEEDINGS OP SOCIETIES. 195 



be obtained. The illusion is due to the glass cylinders virtually- 

 becoming lenses when crossed, and is still further enhanced by the 

 focus of objects behind being within or upon the sui'face of the rods. 

 Mr. Hennah would not be imderstood to maintain that because in 

 these photographs he had obtained jjseudo-heads no beaded structui'es 

 existed. He believed in some cases they might exist, although in 

 the majority he was of opinion that they were phantoms of refraction 

 and reflexion arising from special illumination of transparent structures 

 by transmitted light. The photographs must fulfil a mission of cau- 

 tion, and he (Mr. Hennah) hoped would lead to more careful exami- 

 nation of debatable things. 



The efi"ects photographed were obtained in the following manner : 



1. Sheet of ground glass close to rods ; illuminated a little 

 obliquely. 



2. Sheet of ground glass 16 inches square about 1 foot behind 

 rods ; slightly oblique illumination. 



3. Same as 2, but with a 6-inch paper cross on ground glass, about 

 6 inches from rods. 



4. Common " knobbed " water-bottle close to rods. 



5. Rods obliquely; a window with curtains. 



6. Eods more oblique than 5 ; an open window quite in focus. 



7. Eods same as last ; same arrangement, but out of focus. 



8. A photograph behind two rods ; placed at right angles, showing 

 distortion. 



It was announced that as there were more papers in the hands of 

 the Secretaries than could be read during the evening, the following 

 would be taken as read. 



A communication from the Eev. Professor Gagliardi, " On Views of 

 Surirella gemma," and another by Mr. Cubitt, " On the Winter Habits 

 of Eotatoria," would be taken as read. 



In alluding to a paper contributed by Lieut.-Col. Dr. Woodward, 

 of the U. S. Army, the Secretary called attention to a series of beautiful 

 photographs of the Podura and other test-objects which Dr. Woodward 

 had presented to the Society. 



Mr. J. Bell then read a paper " On the Microscopic Examination 

 of Water for Domestic Use." 



Dr. Lawson inquired under what powers Mr. Bell had made his 

 examination. 



Mr. Bell said he had used a ^th object-glass and B eye-piece, and 

 a ^th and B eye-piece. 



Mr. Slack attached great value to Mr. Bell's researches. He 

 thought that it would require a very large body of experiments before 

 it would be safe to infer the composition of a solution from the pre- 

 sence of pa,rticular forms of fungi. In comparing some specimens of 

 fungi given to him by Mr. Greenish in solutions of arsenic and strych- 

 nia, with some in silica which he (Mr. Slack) had in dialysed solutions 

 in distilled water, he thought that though the appearances differed to 

 some extent, the plants were of the same kind. As regarded filtering 

 through sand, part of the action was chemical and part mechanical. 

 Passing water through a mass of sand was a very good mode of oxidiz- 



VOL. V. . p 



