When the subject of fluorescence is more thoroughly investigated (it is a discovery of Sir D. Brewster, who was followed by Herschel and Professor Stokes, and is as yet but of yesterday), we may hope for a vast accession to our knowledge of subjects as yet very slightly understood.
At the Bradford meeting of the British Association for the Advancement of Science, in 1873, Dr. Gladstone, F.R.S., demonstrated before the Mathematical and Physical Section what I have said respecting invisible drawings on white cards having produced bold and clear photographs when no eye could see the drawings themselves, and I brought away back to London these photographs, and, for aught I know, may have them still.
To prevent this disquisition from being too dry, I will here introduce a fanciful sketch I wrote àpropos of Dr. Gladstone’s demonstration at the time mentioned:—
A mischievous young lady of scientific proclivities who attended the meeting of the British Association, and who was addicted to practical joking, listened attentively to Dr. Gladstone’s observations upon the properties of quinine referred to, and having carefully noted the discussion that followed, reasoned within herself thus: If solution of quinine can make invisible marks upon paper, which will come out black in a photograph, it ought to do the same when applied to the skin. So she procured some of this solution, and upon her fair brow she painted with it a death’s head and cross-bones. These, of course, were invisible to human vision. Thus prepared, she went to a photographer to have her portrait taken. All went right until the operator went an to develop the plate, when she soon heard an altercation between the photographer and the attendant boy, in which it was evident that the latter was being charged with having coated an old or dirty plate.
A second negative was taken, with this result, that the operator, after bestowing a puzzled, affrighted look at the lady, rushed downstairs to the principal of the establishment. Both returned to the dark room, and a third negative was taken, when it became evident that intense excitement was being produced in the dark room. After an excuse to the lady about there being electricity in the atmosphere, which had affected the chemicals, she was requested to sit once more.
Scarcely had the plate been developed, when both photographer and assistant rushed out from the dark room, pale and excited, and explained that on the brow of the sitter in each negative was emblazoned the insignia of the King of Terrors. The negatives were produced leaving no doubt of the fact. What was to be done?
The sitter hinted something about not being disposed to be made a fool of by one who she was satisfied was a spirit photographer, and that she, for one, would not allow herself to become the victim of such absurdity. This upset the equanimity of the photographer, who expressed his earnest conviction that she was an emissary and personal friend of the common enemy of mankind.
“I shall look in again to-morrow,” said the lady, in her sweetest tones, “if you promise not to play any of your silly ghost tricks upon me.”
“Not for ten thousand worlds,” said the artist, “shall you ever set foot within my studio again!”
“Oh,” she laughingly rejoined, “I shall drop in through the roof and visit you some day when you are disengaged;” and with that she departed.