Tuesday Oct. 26th (Contd) To produce this ring artificially in dummy batteries. The apparatus used is cylindro-conical tintube 1.90 m long + 40 cm in diam. in the cylindrical part which is charged with 150 gr. black powder. It is placed in the entrance of the shelter holding the men that work it. The smoke is produced on receipt of a telephone message from the battery or on hearing the mortar [fire ?].

BC Archives, MS-0392 FRANK SWANNELL PAPERS Box 1 Diary and enclosures, 1915. Volume 4