“"Our Second Experiment", the Professor announced, as Bruno returned to his place, still thoughtfully rubbing his elbows, "is the production of that seldom-seen-but-greatly-to-be-admired phenomenon, Black Light! You have seen White Light, Red Light, Green Light, and so on: but never, till this wonderful day, have any eyes but mine seen Black Light! This box", carefully lifting it upon the table, and covering it with a heap of blankets, "is quite full of it. The way I made it was this - I took a lighted candle into a dark cupboard and shut the door. Of course the cupboard was then full of Yellow Light. Then I took a bottle of Black ink, and poured it over the candle: and, to my delight, every atom of the Yellow Light turned Black! That was indeed the proudest moment of my life! Then I filled a box with it. And now - would anyone like to get under the blankets and see it?"Dead silence followed this appeal: but at last Bruno said "I'll get under, if it won't jingle my elbows."Satisfied on this point, Bruno crawled under the blankets, and, after a minute or two, crawled out again, very hot and dusty, and with his hair in the wildest confusion."What did you see in the box?" Sylvie eagerly enquired."I saw nuffin!" Bruno sadly replied. "It were too dark!""He has described the appearance of the thing exactly!"”

the Professor exclaimed with enthusiasm. "Black Light, and Nothing, look so extremely alike, at first sight, that I don't wonder he failed to distinguish them! We will now proceed to the Third Experiment."</p>
Source: Sylvie and Bruno Concluded (1893), Chapter 21: The Professor's Lecture