But the bottom is not paved, and there are no walls at the sides to secure a uniform depth."

"Then the ca.n.a.l is not twenty-six feet deep, as the affirmative has laid down the law," added Uncle Moses.

"That looks like a lawyer's quibble," replied the captain with a hearty laugh. "You have opened the road for the retreat of the negative."

"The facts set forth by the speakers in our conference fail to be facts," persisted the legal gentleman.

"The fact was given as a general truth that the depth of the ca.n.a.l is twenty-six feet; but I think that no person as reasonable as Squire Scarburn of Von Blonk Park would insist that it should be absolutely of fully that depth in every part in order to comply with the general truth of the statement. The courts don't rule in that way. I read lately of a life insurance company which refused to pay a policy on the plea that the holder had been a drunkard; but the court ruled that the use of intoxicating liquors, or even an occasional over-indulgence, did not const.i.tute a drunkard."

"A wise ruling," added the squire.

"We call a person a good man; but even the affirmative does not insist that he shall be absolutely without sin, stain, or fault in order to ent.i.tle him to this designation."

"There would not be a single good man in that case," laughed the doctor.

"We admit the general truth that the ca.n.a.l is twenty-six feet deep."

"The ca.n.a.l has been dug out of loose sand for the most part, and it would have been impossible to make it of uniform depth. Some of the largest steamers in the world pa.s.s through the ca.n.a.l on their way to India, China, and Australia. The Orient Line has the Ophir, a twin-screw ship, about five hundred feet long, and others nearly as large.

"This big ditch across the isthmus has an average width of three hundred feet, or two hundred less than the length of the Ophir. She could not, therefore, get across the channel. There is a current in this water, and fierce winds sometimes blow across it, and both of these affect the inertia of the vessels. A comparatively small steamer like the Guardian-Mother can be twisted about by these causes, and her bow or her stern may catch on the sloping sides."

"You have made out your case, Captain Ringgold; and the moral is that general truths are not invariably true," said Uncle Moses good-naturedly.

"I only hope we shall not get aground," added Mrs. Belgrave.

"We are fairly started now, and we have Lake Menzaleh on one side, and a low sandy plain, once covered with water, on the other," continued the commander. "It is difficult to believe that the swamp and lagoon on the starboard were once covered with fertile fields, watered by two of the branches of the Nile, where wheat was raised in abundance, from which Rome and other countries were supplied with food."

"What vast flocks of birds!" exclaimed Mrs. Woolridge.

"Those are flamingoes, just rising from their resting-place," added the captain. "They were white just now as we looked at them; notice the color of the inside of their wings, which are of a rose-tinted pink."

"But what became of the wheat-fields that were here?" asked Mrs.

Blossom, after they had observed the wild birds for a time.

"The sea broke in and covered the rich lands with sand and salt; and there are towns buried there now."

"Goodness, gracious!" almost screamed Mrs. Blossom. "There's another steamer sailing on the land!"

"It appears to be so, but is not so," replied the commander.

"It is really so," added Mrs. Woolridge; and all the party gazed with interest at the phenomenon.

"Only apparently so," the captain insisted.

"Please to explain it to us, Commodore," said Miss Blanche, who had long ago applied this t.i.tle to him.

"With pleasure, Miss Woolridge. It is the mirage, from the Latin _miror_, to wonder, which appears to be what you are doing just now. The steamer you see sailing along the sh.o.r.e is an optical illusion, a reflection, and not a reality. Refraction, which is the bending of the rays of light, produces this effect. If you look at a straight stick set up in the water, it will appear to be bent, and this is caused by refraction. The learned gentlemen present will excuse me for going back to the primer of physics."

"We are quite satisfied to have the memory refreshed," replied the doctor.

"The air around us is of different densities, which causes the rays of reflection of our ship to be bent, sending the image up on the sh.o.r.e.

What sailors call 'looming,' often seen on our own sh.o.r.es, is produced in the same way; and we often see an island, or a vessel, looming up away above the water, from which it is sometimes separated by a strip of sky. The mirage is often seen in the desert, with a whole caravan up in the air, sometimes upside down.

"An object is often seen when at a considerable distance from it. In the Arctic regions ships below the horizon, or hull down as sailors phrase it, are revealed to other ships far distant by their images in the air.

From Hastings, on the English Channel, the coast of France, fifty miles distant, from Calais to Dieppe, was once seen for about three hours. In 1854 a remarkable exhibition of the mirage was witnessed in the Baltic Sea from the deck of a ship of the British navy. The whole English fleet, consisting of nineteen sail, distant thirty miles from the point of observation, were seen up in the air, upside down, as if they had been hung up there by their keels.

"The Fata Morgana is a sort of mirage seen in the Strait of Messina. A person standing on the sh.o.r.e sees the images of men, houses, ships, and other objects, sometimes in the air, sometimes in the water, the originals frequently magnified, pa.s.sing like a panorama before the beholder. The vapory ma.s.ses above the strait may cause the pictures to be surrounded by a colored line. When the peasants see it, they shout 'Morgana! Morgana!'"

"What does that word mean?" inquired Miss Blanche.

"The French from which it is derived is '_Morgaine la Fee_,' from a sister of King Arthur of the Round Table, who had the reputation of being a fairy, which is _fata_ in Italian."

"But what is that round table?" asked Mrs. Blossom very innocently.

"You must excuse me, my dear woman," replied the commander, looking at his watch. "The Suez Ca.n.a.l is the subject before us, and I am talking all the morning about other things."

"But it is collateral information, called out by the mirage; and the ill.u.s.trations you mentioned are quite new to me, for one," added Dr.

Hawkes.

"I like this kind of a conference, where the side matters are all explained," said Mrs. Belgrave. "But it is a pity the boys are not here, for they are not getting any of the cream of this conference so early in the morning."

This was enough for the commander, coming from her; and he immediately hastened to the stern of the ship, where he hailed the Maud, and ordered her to come alongside. The four sailors who had attended the party in the excursion to Cairo and up the Nile were directed to go on board of the tender, and take the places of the "Big Four." The Guardian-Mother had to go into a "siding" to permit a steamer to pa.s.s her at this point, and the transfer was easily made.

However it may have been with the others, Louis Belgrave was glad to get back to the ship, where he could sit by the side of Miss Blanche, and answer the many questions she was continually asking; for she had an inquiring mind. As she often remarked, Louis always seemed to know all about everything. Perhaps if he had been with the party all the time, he might have lost some portion of his reputation as a walking encyclopaedia; for when he was to be with her on any excursion, he took extraordinary pains to post himself upon the topics likely to be considered.

"You notice that post near the siding," said Captain Ringgold when the party on the promenade had been re-enforced by the addition of the young men, and the steamer began to move again. "That is one of the five kilometre posts; and you will find them all the way to the Red Sea."

"What is a kilometre?" inquired Mrs. Woolridge.

"I have talked so much that I will ask Mr. Belgrave to explain it,"

replied the captain.

"It belongs to the French metrical system, which most people have come to believe is the best in the world. I suppose everybody here knows what a meridian is, for it was explained when we were talking about great circles and geographical or sea miles. A meridian is a great circle reaching around the earth, and pa.s.sing through the equator and the poles. A quadrant of a meridian is the quarter of a meridian, extending from the equator to either pole. This is something that does not vary in extent. A commission of five learned men, especially in mathematics, was appointed by the French Academy, at the instance of the government, to adopt a standard, and they made it a metre, which is the ten millionth part of the quadrant of a meridian. The metre is 3.28 feet of our measure, with five more decimal places after it.

"Ten metres make a decametre, and one thousand metres make a kilometre, and ten thousand metres make a myriametre. Without bothering with all these decimals, a kilometre is about five-eighths of a mile. Five kilometres make three miles and one-tenth, which is the distance between these posts," said Louis in conclusion.

"How came you to be so ready with your explanation, Mr. Belgrave?" asked Miss Blanche, with a pleasant smile of approval.

"Captain Scott had talked the whole thing to us on board of the Maud while he steered the steamer," replied Louis.

"But he knows five times as much about metres as I do; for I could not have explained the meridian business," interjected the captain of the Maud.

"Five miles an hour is slow travelling; but it enables us to see the country, and also to talk about it," said Dr. Hawkes.

"If you don't mean that I am talking too much, Doctor"--

"I certainly do not mean that, and I hope you will keep it up,"

interposed the surgeon.

"Then I will say that the ca.n.a.l is run on the 'block system,' except on the lakes, where the ships can go at full speed," added the commander.