In some other countries, however, the people are not so fortunate.  In Senegal, at certain seasons, the inhabitants are driven from their habitations by the clouds of mosquitoes which spread over the land, and are forced to take refuge on high platforms, under which they keep fires continually burning.

The smoke from these fires will keep away the mosquitoes, but it cannot be very pleasant to the Senegalians.  However, they become used to it, and during the worst of the mosquito season, they eat, drink, sleep, and enjoy themselves to the best of their ability on these platforms, which for the time become their houses.

[Illustration:  A SMOKY DWELLING.]

It would probably seem to most of us, that to breathe an atmosphere constantly filled with smoke, and to have it in our eyes and noses all the time, would be almost as bad, if not quite, as suffering the stings of mosquitoes.

But then we do not know anything about Senegalian mosquitoes, and the accounts which Dr. Livingstone and other travellers give of the insects in Africa, ought to make us feel pretty sure that these woolly-headed folks on the platforms know what is good for them.

THE CANNON OF THE PALAIS ROYAL.

[Illustration]

In the Gardens of the Palais Royal, in Paris, there is a little cannon which stands on a pedestal, and is surrounded by a railing.  Every day it is loaded with powder and wadding, but no one on earth is allowed to fire it off.  However, far away in the realms of space, ninety-three millions of miles from our world, there is the great and glorious Sun, and every day, at twelve o’clock, he fires off that little cannon, provided there are no clouds in the way.  Just before noon on bright days, the people gather around the railing, with their watches in their hands,—­if they are so lucky as to have watches,—­and precisely at twelve o’clock, bang! she goes.

The arrangement which produces this novel artillery-practice is very simple.  A burning-glass is fixed over the cannon in such a manner that when the sun comes to the meridian—­which it does every day at noon, you know—­its rays are concentrated on the touch-hole, and of course the powder is ignited and the cannon is fired.

Most boys understand the power of a burning-glass, and know how easily dry grass or tinder, or a piece of paper, may be set on fire by a good glass when the sun is bright; but they would find it very difficult to place a glass over a little cannon so that it would infallibly be discharged at any set hour.  And even if they could do it, they would not be sure of their cannon-clock being exactly right, for the sun does not keep the very best time.  He varies a little, and there is a difference between solar time and true time.  But the sun is always near enough right for all ordinary intents and purposes.

I know boys—­lazy fellows—­and some girls of the same sort, for that matter,—­who, if they could, would have, just outside of their school-doors, one of the largest cannon, which should go off every day at the very earliest hour at which school would let out, and which should make such a tremendous report that it would be impossible for the teacher to overlook the time and keep them in too long.