i88o.] The Phenomena of Fluorescence. 627 
piece of what is commonly termed canary glass —i.e. f glass 
coloured with an oxide of the metal uranium,— it will be 
seen to glow as it were with rich greenish yellow rays, just 
as though it were itself a source of light ; or if we take a 
solution of a uranium salt (the normal acetate) the pheno- 
mena are very striking when examined _ under the same 
conditions, and still more so by the eledtiic light. But the 
salts of aniline— a substance which is the parent, so to 
speak, of mauve, magenta, and other brilliant colours are 
singularly rich in exhibiting these effects. # 
A very beautiful experiment may be performed with the 
aniline red ink now so commonly in use. It affords, at one 
and the same time, an admirable illustration of Prof. Tom- 
linson’s submersion figures and of the phenomena under 
consideration. If we take a long cylindrical glass vessel, or 
one with parallel sides, fill it with water, which is . allowed 
to settle, and then gently deliver a drop of the red fluid to the 
surface/ the drop begins to contract, and slowly from its 
centre descends in the form of a tube ; the denser parts of 
the colouring-matter presently form a thick circular rim at 
the end of the tube,— but this is only for a moment, for a 
wavy edge appears upon this rim, then expands into a tii- 
angular parachute with a thickened edge, and from the 
extremity of each corner two or three smaller tubes descend , 
these in like manner pass through the same phases as the 
parent stem or tube. When this beautiful figure is viewed 
by transmitted light it exhibits the ordinary bright red 
colour ; but when placed against a very dark background, 
and looked at from a little distance and at an angle, it is 
seen to be of a brilliant green* very like a curious sea-weed 
serenely floating in a summer sea. Viewed vertically it 
presents a most singular shape, and glows with a fine golden 
tinge. Chlorophyll, the green colouring-matter of leaves 
before mentioned (those of the nettle are preferred) by 
reflected light is a bright green ; but when a beam of white 
light concentrated by a lens is sent through it, the path of 
the beam is of a blood-red hue. 
Crude resin oil, which is almost opaque, presents a deli- 
cate sky-blue fluorescence at its surface and the side opposite 
the light One investigator has shown that some colouring- 
matters obtained from different woods, which though soluble 
in alcohol, alkaline solutions, or in alum, and not in this 
way sensitive, are very brilliantly fluorescent when dissolved 
* The brilliancy of colour, of course, depends on the amount of diffused day 
light. The effects in each case are best seen on a bright day. 
