58 



BULLETIN OF THE BUKEATJ OF FISHERIES. 



light, and estimated that in good weather it would be possible to do this at depths 

 of 7 or 8 meters. 



Although his flash-light apparatus proved to be unnecessary in shallow water 

 and was subsequently abandoned as cumbersome and dangerous, it merits a 

 word of description. His figure of it is reproduced in figure 8. In its final form it 

 consisted of a cask of about 200 liters capacity closed at both ends, but with 

 the lower end perforated by holes to permit the entrance of sea water. A bell jar 

 of 5 or 6 liters capacity is held tightly against the upper end of the cask by means 

 of the adjustable frame shown in the figure. The cavity of the jar communicates 

 freely through many openings with that of the cask, and both are filled with air. 



Within the bell jar is an alcohol lamp, and at the 

 side of this is a metal reservoir (not shown in the 

 figure), covered with asbestos and filled with mag- 

 nesium powder. One end of a metal tube opens 

 opposite the middle of the flame of the alcohol 

 lamp (shown lighted in the figure) and communi- 

 cates freely with the reservoir above. The other 

 end of the tube extends into the cask, and is there 

 connected to a rubber tube which extends through 

 the side of the cask (at C in fig. 8) and ends in 

 a large rubber bulb. To use the apparatus, the 

 reservoir is filled with magnesium powder and 

 the alcohol lamp lighted, then the bell jar is 

 fastened in place and the cask, heavily weighted 

 at the bottom, is lowered into the water and set 

 wherever needed. The air in the bell jar and cask 

 is enough to keep the alcohol lamp burning for 

 some time. To produce the flash it is merely 

 necessary to press the bulb, when the magnesium 

 powder, which has fallen from the reservoir into 

 the tube, is blown against the flame from the end 

 of the tube and ignited. This operation may be 

 repeated as long as the lamp remains burning and 

 the reservoir contains magnesium. It is of course 

 necessary to operate the shutter of the camera 

 simultaneously with the flash. 

 Boutan (1900) describes and illustrates another illuminating apparatus which 

 consists of two powerful arc lamps inclosed in water-tight jackets of heavy metal, 

 designed to withstand the pressure of the water at a depth of 50 meters or more. 

 Each jacket was pierced by an opening into which was fitted a condensing lens, 

 by which the emerging light was concentrated upon the object to be photographed. 

 The two lamps were rigidly attached to the camera support and were supplied, 

 through a cable, with current from storage batteries on board the boat. The 

 same cable carried also an insulated wire through which an electro-magnet 

 actuating the shutter of the camera could b'e controlled. The camera with lamps 

 attached was lowered into the water. When the camera was on the bottom the 

 lamp circuit was closed by means of a switch on board the boat, and when it was 



FIG. 8. Boutan's apparatus for using a mag- 

 nesium flash-light under water. The reser- 

 voir for the magnesium powder, the rubber 

 bulb, and th weights used to steady the ap- 

 paratus are not shown in the figure. (Copy 

 of fig. 3 in Boutan, 1893.) 



