1658 



Journal of Applied Microscopy 



A heavy cylindrical bar of hard wood two inches in diameter, and four feet 

 eight inches long, is affixed vertically to the side of the table opposite to the side 

 into which the photographic plates are inserted. This bar passes through a 

 block which may be moved, in horizontal grooves, from one end of the table to 

 the other. The bar may also be rotated on a vertical axis, and moved up and 

 down vertically any desired distance. It is fixed by means of a brass friction 

 clamp. Two secondary blocks, one on either side of the first, serve as fixed 

 points to which the vertical arm can be returned if displaced for any reason. 



From the upper end of the vertical arm there extends a horizontal arm, also 

 of hard wood, long enough to permit the X-ray tube to be suspended from it by 

 means of a heavy wooden clamp over any part across the width of the table. 



Fig. 2. — The table ready for an exposure. 



Both vertical and horizontal arms are marked off in inches. The scale on 

 the vertical arm indicates the distance of the anti-cathode of the tube from the 

 photographic plates. The clamp for the tube hangs vertically downward from 

 the horizontal arm, and at its lower end bears a pair of grooved jaws padded 

 with rubber, so placed that when the horizontal arm is at right angles to the long 

 axis of the table the X-ray tube is very firmly held, with the plane of the anti- 

 cathode at an angle of 45° with the surface of the table, and with the long axis 

 of the tube parallel with the long axis of the table. The construction of this 

 gallows frame, as it may be called, is heavy, for the sake of rigidity. Metal 

 should be avoided as far as may be in its construction. 



Stereoscopic X-ray pictures are taken as follows : A photographic plate, in 

 its envelopes, is inserted into the carrier ; the elbow of the toggle-joint is 

 straightened, thus raising the plates into contact with the pegamoid covering of 



