Many of our readers may be glad to know an easy way to make an envelope of any shape or size.
This diagram speaks for itself. When the lines A B, A C, D B, D C have been drawn, the corners of the rectangle, H E G F, are folded over, as shown by the dotted lines, after the corners have been rounded, and the margins touched with gum.
No. CI.—SQUARING AN OBLONG
The diagrams below will show how a piece of paper, 15 inches long and 3 inches wide, can be cut into five parts, and rearranged to form a perfect square.
A PLAGUE OF BLOW-FLIES
The following astounding calculation is answer enough to a question put by one of the authors of “Rejected Addresses:”—“Who filled the butchers’ shops with big blue flies?”
A pair of blow-flies can produce ten thousand eggs, which mature in a fortnight. If every egg hatches out, and there are equal numbers of either sex, which forthwith increase and multiply at the same rapid rate, and if their descendants do the like, so that all survive at the end of six months, it has been calculated that, if thirty-two would fill a cubic inch of space, the whole innumerable swarm would cover the globe, land and sea, half a mile deep everywhere.