The History and Properties of the Rontgen Rays. 59 



that, in fact, they were about eight octaves above the green in 

 our colour scale. There was reason to believe that a portion 

 of the gap between the ultra violet and X rays had been filled. 

 Becquerel, inside the past year, had shown that if uranium salts 

 were scattered over a wooden box containing a photographic 

 plate, and exposed to sunHght, the salts acquired and retained 

 for more than fifteen days the power of giving out rays, which 

 passed through the box and blackened the plate. He had also 

 proved that these were most probably ultra violet rays of very 

 high number of vibrations. 



At this stage a number of pictures were thrown upon the 

 screen for the purpose of showing what are the applications of 

 X rays in surgery. They could all see, said Mr. Finnegan, 

 that physical science had received by this discovery an agent 

 which promised to be of great service in investigating some of 

 the outstanding problems in the properties of matter. 



The lecture, which was profusely illustrated, was listened to 

 with great attention ; and 



On the motion of Mr. John Brown, seconded by Professor 

 FitzGerald, a vote of hearty thanks was passed to Mr. Finnegan. 



