PRESIDENT’S ADDRESS. 41 
as madder-growing has become unprofitable, and, therefore, 
practically extinct. In the absence of any description of 
the reactions by which it is made, the report, I think, 
requires confirmation. 
TRANSPARENCY OF THE CHEMICAL ELEMENTS TO THE RONTGEN 
: RAYS. 
Réntgen found that the rays from a Crooke’s tube passed 
freely through black card-board, which is impervious not 
only to ordinary luminous and thermal rays, but also to the 
other invisible rays beyond the violet end of the spectrum, 
which are so active in producing fluorescence and photo- 
graphic effects. 
These invisible (X) rays passed freely through the 
opaque card-board and produced luminous effects upon 
screens coated with fluorescent substances, and, further, 
photographs could be taken by their aid on ordinary plates ; 
afterwards it was found that they would go through many 
other substances, including sheets of metallic aluminium, 
and that they were not deflected by a magnet. They also 
dis-electrify an electrified body, and can neither be reflected 
nor refracted. 
Although a perfect deluge of papers and scientific litera- 
ture upon the X and other rays has appeared within the 
last two years, and an enormous number of people are 
experimenting upon these rays—there are even special 
Réntgen Ray Societies—yet I do not intend to go into the 
general subject, as it belongs to the domain of physics 
rather than chemistry—but as one of the most striking 
properties of the rays is that they pass through plates of a 
large number of metals, and still retaim their chemical 
action upon salts of silver, and are capable of producing 
photographic effects, they are of interest from a chemical 
point of view. 
The great interest and popularity which this subject so 
suddenly acquired was undoubtedly largely due to the fact 
that the flesh is more transparent to them than the bones 
of the skeleton; hence it is easy to see the outlines of the 
