Part 21

109. A locomotive with a truck is travelling over a straight level line at the rate of 60 miles an hour. A man standing at the extreme rear of the truck casts a small stone into the air in a perpendicular direction. The stone travels upward at an average rate of 30 feet per second for 3 seconds; the height of the man’s hand from ground when the stone leaves is 15 feet. At what distance behind the train will the stone strike the ground in its descent?

A Tombstone in an English Cemetery.

Many quaint and puzzling epitaphs are often to be seen engraved on several of the tombstones in some of the old cemeteries at Home. The adjoining illustration represents a tombstone in the old burial-ground of London--Kensal Green. It might “liven” up the reader to discover the scheme of kindred as given in the inscription.

SACRED TO THE MEMORY OF

TWO GRANDMOTHERS WITH THEIR TWO GRANDDAUGHTERS; TWO HUSBANDS WITH THEIR TWO WIVES; TWO FATHERS WITH THEIR TWO DAUGHTERS; TWO MOTHERS WITH THEIR TWO SONS; TWO MAIDENS WITH THEIR TWO MOTHERS; TWO SISTERS WITH THEIR TWO BROTHERS YET, BUT SIX CORPSES IN ALL LIE BURIED HERE-- ALL BORN LEGITIMATE FROM ERROR CLEAR.]

EASILY ANSWERED.

“Johnny,” said his teacher, “if your father can do a piece of work in seven days, and your uncle George can do it in nine days, how long would it take both of them to do it?”

“They’d never get it done,” said Johnny; “they’d sit down and tell snake-yarns.”

110. A well is to be sunk by 12 men, in groups of 4 each, in 12 days. The groups work in the ratio of 6, 7, and 8; when half the task is done rain sets in and prevents them working for 2 days, in which time one man of the first, 2 of the second, and 3 of the third group go away, leaving the remainder to finish the job. What extra time did they work?

“TAKE CARE OF THE PENCE, &c.”

One of the most startling calculations is the following:--

A penny at 5 per cent. compound interest from A.D. 1 to 1890 would amount to £10,000,000,000,000,000,000,000,000,000,000,000,000, i.e., Ten Sextillions of pounds, or more money than could be contained in One Thousand Millions of Globes each equal to the Earth in magnitude, and all of solid gold.

111. On a flagstaff consisting of an upright pole (6 feet of which is underground) is a cross-yard 24 feet long; the latter is fixed at a distance of one-third of the length of the visible part of the pole from the top; passing from the top of the pole to the ends of the yard are ropes, forming stays whose falls or ends reach to the ground on either side of the pole, and it is found that these falls just reach the base of the pole. The total length of rope in the aforesaid stays is 40 feet. Supposing that the top diameter of the pole is one-third of that at the extreme base, and that the whole length of rope used is 54,177 times the base diameter of the pole, what would the pole cost at 1 penny per 100 cubic inches?

TEACHER--“Your writing is fairly good, but how do you account for making so many mistakes in your spelling?”

SCHOLAR--“Please, ma’am, I had chilblains on my hand?”

112. Put down 4 marks (| | | |), and then require a person to put 5 more marks and make 10.

“KEEP YOUR HAIR ON.”

113. Supposing there are more persons in the world than anyone has hairs on his head, there must be at least two persons who have the same number of hairs on the head to a hair. Explain this.

114. Show what is wrong in the following:--

8-8 = 2-2, dividing both these equals by 2-2 the result must be equal; 8-8 divided by 2-2 = 4, and 2-2 divided by 2-2 = 1, therefore, since the quotients of equals divided by equals must be equal, 4 must be equal to 1.

“GLAD TIDINGS.”

Many will be surprised to hear that there is Scriptural authority for advertising. Advertising not only has Scriptural authority, but it is of very respectable antiquity as well. If you will look in Numbers XXIV., 14, you will find Balaam saying “Come now, and I will advertise,” and Boaz says in Ruth IV., 4, “And I thought to advertise.”

OPTICAL ILLUSIONS.

Illusions of the Eye are numberless, and afford a wide field for experiment. Some people are left-eyed, others right-eyed, and very few use both eyes equally. It is impossible to tell how far they really do deceive us unless they have been tested in the proper manner. For instance, if you ask anyone to what height a bell-topper would reach if placed on the floor against the wall, nine times out of ten the height guessed will be half as much again as the real height of the hat. Everyone seems to over-estimate the proper height.

Another favourite illusion is to ask a person to mark on the wall a height from the floor which would represent the length of a horse’s head: here the majority guess far too little--for a horse’s head is much longer than most people imagine, ranging from 25 to 34 inches. In a recent experiment 5 persons out of 6 under-estimated the proper height.

Here are two triangles. Which is the one whose centre is the better indicated? (It looks like A, but it is B).

Again: Out of the two straight lines C and D which is the longer? (By measurement we see they are both the same).

Guess, by eye-measurement only, the longest and shortest of the three lines marked A A, B B, and C C. When you have done guessing measure, and see how much you are out.