412 



Mr. J. H. Vincent on the 



Diagram of Apparatus. -L nat. size. 



T. Mercury trough. 



A. Standard of retort-standard. 



B. Wooden block through which passes the bent down portion of A, 



C. Upper bar of wooden stand. 

 IR. India-rubber loop. 



S. First spark-gap. 

 LL. Lenses. 



D. Camera. 



F. Tuning-fork and stand. 



