1 1 24 BULLETIN OF THE BUREAU OF FISHERIES. 



passes across its face. The rate at which the curtain moves and the width of 

 the slot may be regulated. When the operator with the mirror set at m has 

 focused the object and brought it into the desired position on the ground glass, 

 he presses the button which releases the mirror. At the instant the mirror 

 reaches the position m' it releases the mechanism which actuates the shutter, 

 and the roller with its slot travels across the face of the plate, so that the 

 exposure is made. It is unnecessary to dwell here on all the advantages of 

 this form of camera. The feature of importance is that the camera permits 

 the object to be kept in focus up to the instant of exposure and then permits 

 the exposure to be made without removing the ground glass and inserting the 

 plate, as is necessary in the ordinary form of camera. 



In using this form of camera for photographing objects under water the 

 writer inclosed it in a water-tight box of galvanized iron. This box, shown in 

 figure 7, plate cxvii, is provided at one end with a plate glass through which the 

 picture is taken. In the top of the pyramidal portion of the box which covers 

 the hood of the camera there is a second plate of glass which does not show 

 in the figure and through which the operator looks into the hood of the camera 

 and examines the image on the ground glass. The camera is focused from 

 the outside with the right hand by means of a milled head, from which a stem 

 extends through a water-tight stuffing box to connect with the focusing screw 

 of the camera. The exposure is made by pressing a pin which is on the oppo- 

 site side of the box from the milled head shown in the figure and which also 

 extends through a stuffing box to the interior of the water-tight box, where it 

 actuates the mechanism by which the mirror of the camera is set in motion. 

 The top of the box is held in place against a rubber gasket by eight thumb- 

 screws by the use of which the joint between the box and the lid is rendered 

 water-tight. When the box is in use its bottom must be heavily weighted with 

 lead to submerge it. 



In figure 8, plate cxvii, is shown the method of using the reflecting camera 

 when inclosed in the water-tight box. The photographer is wading near a coral 

 reef. The body of the box inclosing the camera is submerged, but the pyram- 

 idal top of the box inclosing the hood of the camera projects above the 

 surface of the water. Through the glass in the top of the hood the photographer 

 is viewing the image on the ground glass, while he focuses the camera with the 

 right hand and is prepared to make the exposure with the left hand. When the 

 exposure has been made the water-tight box must be taken from the water and 

 opened in order to change the plate before making a second exposure. 



If the water-tight box is made strong enough to resist the pressure of the 

 water the photographer may descend in a diver's suit and may, with the appa- 

 ratus described, make photographs at considerable depths. If the camera box is 

 set on a tripod time exposures may be made with an apparatus of this type, but 



