.S7A' WILLIAM .s7/-;.)//-:.V\, l-'.R.s. 



313 



thought they were perhaps of all metallic surfaces the least apt to 

 tarnish. Nickel was as hard as hardened steel-, and it seemed to 

 ivmuin perfectly bright under all atmospheric influences, even in 

 rooms where sulphuretted hydrogen was present. 



There was one other light, which had occupied his attention 

 during the last twelvemonths, to which he would refer : Mr. 

 Thomas Stevenson, of the Northern Lights, had proposed to 

 establish flashing lights (that was to say, lights giving out flashes 

 at certain intervals) upon beacons and buoys ; and Mr. Siemens had 

 been applied to with a view to accomplish that object. The 

 source of light was to be upon the land, because there were periods 

 of the year when a landing could not be effected with safety at the 

 beacons or buoys ; and the source of light which naturally 

 suggested itself under these circumstances was electricity. The 

 apparatus that had occurred to Mr. Stevenson was the Ruhmkorff 

 coil placed upon the land, and communicating with the beacon 

 through a cable ; but the preliminary experiments at once showed, 

 that the discharge of a Ruhmkorff coil would be absorbed in a 

 cable of only 100 yards in length, and that no spark would be 

 produced on the beacon. The next thing tried was to place the 

 coil on the beacon, and to send simply the battery current through 

 the cable : a cable having a large metallic section was taken, but 

 nevertheless the absorption was such, that no perceptible spark 

 could be produced. Under these circumstances the idea suggested 

 itself to him, that a simple metallic circuit might be established 

 through the coils of an electro-magnet, and that the extra current 

 produced in breaking that circuit would produce a flash, close to 

 the electro-magnet upon the beacon, which would be increased 

 rather than otherwise by the accumulated charge in the connecting 

 cable. If this could be practically accomplished, then the light 

 might be placed at a considerable distance from the shore, without 

 destroying the battery effect which had to be transmitted from the 

 land through a cable. The apparatus was not perfected at once ; 

 but he had placed one on the table which would accomplish the 

 object in view. It comprised a heavy electro-magnet, the coils of 

 which were supposed to be in communication with a battery on land 

 through a cable. A clock-work apparatus on land established the 

 electric circuit through the cable at certain predetermined intervals. 

 The electric circuit through the cable was, however, not complete, 



