Intelligence and Miscellaneous Articles. 555 



APPLICATION OF THE ELECTRIC LIGHT (gEISSLEr's TUBES) FOR 

 LIGHTING UNDER WATER. BY M. PAUL GERVAIS. 



Of late years the electric light has been used for illumination 

 under water. In the Channel and in the Mediterranean attempts 

 were made by means of water-tight receivers of glass, in which 

 works a regulator for bringing in contact carbons made incandescent 

 by a battery, the elements of which are on board a vessel on which 

 the trials are made. The part serving as lantern is sunk under water. 



In some cases these attempts have been successful, and the light 

 thus produced has been utilized either for submarine works or in 

 fishing, which this method seemed to render more productive by 

 attracting the fish. Yet the use of such apparatus is costly, and the 

 manipulation difficult ; moreover the light is in many cases too 

 bright, and, besides, the entire arrangement is liable to numerous 

 accidents, such as, for instance, the spilling of the liquid owing to 

 the motions of the vessel. 



There are, moreover, circumstances in which a less brilliant light 

 is sufficient and even preferable. It would, therefore, be useful to 

 construct an apparatus capable of working under w 7 ater, and such 

 that its total immersion would not stop its working. I thought that 

 these results might be arrived at by means of Geisslers tubes, placing 

 them in connexion with an exhausted receiver containing the ele- 

 ments of a battery and a coil for producing the electrical current by 

 which these tubes are made luminous ; and M. Ruhmkorff has con- 

 structed for me the following apparatus : — 



Our receiver is a sort of bronze box mounted on four small feet, 

 and the cover of which is made to fit hermetically by means of 

 screws and of a vulcanized india-rubber washer. A ring on the 

 cover serves to suspend the entire apparatus. The exhausted 

 box contains two bichromate-of-potash elements closed in their turn 

 by plates. The poles of the current furnished by the element can 

 at pleasure be connected with the coil, and the induced current, by 

 means of insulated wires, passes through the bottom of the apparatus 

 to a Geissler's tube. This tube, of an appropriate form and filled 

 with carbonic acid, is enclosed in a thick glass cylinder provided 

 with copper armatures, and into which water cannot penetrate. This 

 is the illuminating part of the apparatus. 



With this instrument a soft but distinct light is obtained, re- 

 sembling that which military engineers and miners now use. In 

 some respects it resembles that which phosphorescent animals emit, 

 though it is more intense. It can be seen at a considerable distance, 

 even when the apparatus is worked under water at a depth of seve- 

 ral metres. It cannot be doubted that it will attract fish as does the 

 phosphorescence of certain species, and it might also be used to illu- 

 minate closed spaces situate below the surface of the water, or for 

 making floating signals. 



Captain DerouLs has seen this apparatus work in the port of Cette 

 last September. In this experiment the apparatus was immersed for 

 nine hours, and it illuminated during six hours under these conditions. 

 The duration of its phosphorescence may be greater. A second trial 

 at Port Vendres also succeeded. — Comptes Rendus, March 27. 



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