1895.J MICROSCOPICAL JOURNAL. 185 



see lines. I place a yellow glass anywhere in the path of 

 the ray. The lines disappear. 



C I put on b with day-light and I see lines ; with light 

 from petroleum oil they disappear. 



D. I get the lines with greater obliquity of illumina- 

 tion with petroleum light, but with gas light they dis- 

 appear. 



These had been my experiments up to date. Now I 

 tried the spectrum from a flint glass prism in the after- 

 noon when there are the least actinic rays, did resolve 

 in the blue ray and did not anywhere else in the spec- 

 trum. The light at the same time was very faint. In 

 the yellow ray the hexagons became strongly marked 

 lines showing there was more light but not so much de- 

 fining power. In the red ray all was confusion. Using 

 spectrum I could resolve certain objects in the blue ray 

 with a l-5th. I could only do with a l-15th with the or- 

 dinary light. Dr. R. K. Browne having told me he could 

 resolve the Amphipleiira pellucida when mounted dry, un- 

 covered on mica not on glass, I took two drops from the 

 same bottle (Moran Lake 1865, R. C. Gr.) of Navicula 

 rhomhoides and mounted on glass and mica uncovered, 

 dry. Using spectrum in the blue ray I hexagonized with 

 a 4-lOth only to be done in ordinary light with a l-15th. 

 I tried the spectrum from a gum copal prism also but it 

 was so small and faint from defective polishing, that no 

 different results were arrived at. 



A few days back I was taking a photograph and used 

 a very faint petroleum oil lamp in my dark room ; it was 

 behind the bath and preparing the plate. I removed it 

 only twice from the bath and then introduced it again 

 very quickly so that it was exposed to the light of the 

 lamp only a very short time, yet there was a picture of 

 the dipper on the plate taken by the light of the lamp." 



"October 21st, 1865. On my S. and B. Educational 



