30 PHYSICAL RESEARCH 



bulb is placed a foot or so above the hand and 

 made to send out its rays, the plate is acted on in 

 varying degrees. Where nothing but the thin 

 paper is in the way of the rays the effect on the 

 plate is strong. The paper is thin and contains 

 no heavy atoms. Where the rays pass through 

 flesh they are weakened before they get to the 

 plate because the flesh, though it contains no 

 heavy atoms, is sufficiently thick to have a screen- 

 ing effect; consequently there is a shadow on the 

 latter when it is developed. Where the rays have 

 to traverse the bones they are much absorbed, 

 and the action on the plate is small. On the whole 

 there is a weak shadow of the flesh upon the plate, 

 and a strong shadow of the bones within that. 

 These are the effects which the surgeon finds so 

 useful. Before he tries to set the limb, or to cut 

 down to remove a foreign body, he knows exactly 

 what is wrong; he has, indirectly it is true, seen 

 the mischief and had time to consider his plans 

 before the moment when he must work quickly 

 and every faculty must be free to do its best. It 

 is a marvellous power to possess. 



The rays were discovered in 1896. Suppose 

 that in 1894 the surgical profession had asked if 

 science could furnish the powers just described. 

 We are trying to reverse what actually happened, 

 and to see if things could have taken place as they 

 did "Through the Looking Glass"! Now in the 

 first place we cannot imagine how the profession 



