Science. 



N. S. Vol. III., Plate 4. 



Fig. 1. The varying transparencies of a number of substances for the X-rays. At the top is a book ; to 

 its right a 'rubber' cork about 3 cm. high; just below tliat a 'cork' cork of equal thickness, but of far 

 greater transparency ; in the right lower corner is a crystal of Iceland spar, 1 cm. thick; in the left lower 

 corner a loop of aluminium wire enclosing little Canada balsam (shows faintly ) ; between the loop of wire and 

 the spar may be very faintly seen a very thin piece of mica; abo\'e this is a hard rubber tube containing water 

 with cork stopper; the superior transparency of cork to that of water is well shown where the cork is pressed 

 into the rubber tube. (E. B. Feost. ) 



Fig 2. Coins in leather purse (A. W. Goodspeed). Fig. 3. Pins in cushion (A. W. Goodspeed). 



