64 THE ROYAL SOCIETY OF CANADA 
The “reflected” radiation from lead can be determined by sub- 
traction, and on multiplying by the square of the distance and taking 
logarithms for ordinates, a curve is obtained indicating the difference 
between two expotentials. The straighter portion gives a value of 
pt = -0058 cm.~'. In some cases the lead reflection increased the 
ionization 88 per cent, and copper 64 per cent. We may compare the 
results of Kovarik, when aluminium absorbed the # rays from radium 
E, namely 
air behind #— 42-4 cm.—! 
lead “ p= 44.8 « 
lead —air fim bile Rss 
