259 



^A•ooLk'll lihick liy two biiidinj;' posts in order to make connection with the 

 batter}'. The photographic plate Avas so mounted back of a block of 

 wood about 25 cm. long. 14 cm. wide and 4 cm. thick with a hole 2^2 

 cm. iu diameter that it could be slid past the opening and a number of 

 exposures made upon one plate. 



MS RiAP, 

 20SEC. 



PL/JTE. I, 



The tirst two photographs taken with the apparatus just describei^l 

 with the time of exposiu-e and current as indicated. There is very little 

 if any difference between those niarkr<l .\ and the others. Those marked 

 N are exposures Avithout a lead screen inserted between the soiu'ce and 

 the platinum AA'ire. 



