A Voyage round the World / A book for boys

by William Henry Giles Kingston

“No, indeed, I cannot,” answered Silas. “I’ve met with it more than once. It is a very curious phenomenon.”

“They do say it comes off from the coast of Africa,” remarked Ben Yool, who was at the wheel, and from his age privileged to speak on such a matter. “It’s full of red sand, and I’ve seen it covering the decks in some parts as if a man had been scraping a red holystone over them.”

We were still discussing the subject, when Captain Frankland came on deck. He listened for some time to what we were saying.

“I am glad to hear you discuss the subject, my lads,” he remarked in a kind voice. “Though you are wrong in your conjectures, if you will attend, I will try and explain what I know about the matter. It is a very important one, for by means of this dust—for dust it is—which fills the air, philosophers have been able to determine in part the difficult problem of the track of the winds in their circuits. How is this? you will say. Dust coming from one place surely cannot be distinguishable from dust coming from another. To the ignorant man it is not, but to the man of science it is. There are certain minute animal productions called infusoria and organisms peculiar to each portion of the globe. The expression is, the habitat of such infusoria is such or such a place. These infusoria can only be distinguished by a most powerful microscope. Professor Ehrenberg, who has devoted his attention to the subject, has examined specimens of the dust which is now falling on our decks. He found it composed of dry infusoria, the forms of which are found not on an African desert, but in the south-east trade-wind regions of South America.”

“South America, father!” exclaimed Jerry, pointing with his hand to the south-west. “How can those clouds of red dust come all the way out here in the teeth of the north-east trade-wind?”

“What becomes of the north-east trade-wind when it reaches the end of its journey, and where is that end think you, my boy?” asked Captain Frankland. Jerry looked puzzled, and I had not a notion to give forth on the subject. “I will try and explain the matter; but when you can obtain a work, written by Lieutenant Maury, of the American navy, you will comprehend the subject much better,” said Captain Frankland. “There are three calm regions or belts surrounding the globe—one under the equator, and one in each hemisphere, under the tropics of Cancer and Capricorn, which you have heard spoken of as the horse latitudes. Between these two belts blow the north-east and south-east trade-winds, meeting at the equatorial belt. Now, when they get there, instead of causing a whirlwind, the excessive heat causes the particles of which they are composed to expand and rise, gradually producing a calm. After rising a certain height, they again commence moving round the globe. Which course they took it was difficult to say, till we find these clouds of red dust carried along in an upper region of the atmosphere from south-west to north-east; for not only are they found here, but up the Mediterranean and across Switzerland. They are raised into the atmosphere probably by whirlwinds which occur during the vernal equinox, which is the dry season, from the valley of the lower Orinoco. Thus, had a label been attached to each particle of which the wind is composed, to show whence it came, the problem could not have been more perfectly solved.”

While the captain was speaking, Mr McRitchie came on deck, and collected in sheets of paper a quantity of the red dust. “It will be prized by some of my scientific friends at home,” he observed; “and even the unscientific may value a substance which has travelled half round the globe high up in the atmosphere.”

“There is another substance, doctor, which travels farther, and is of much greater use to man; and yet how little he troubles his head to consider where it comes from,” remarked the captain.

“What do you mean, sir?” asked the doctor, a little puzzled I thought.

“Water,” answered Captain Frankland. “Remember those dense fogs, like wet blankets, which so continually rise in those calm regions to the south of us; they are caused by vapours rising from the sea, and leaving its salt behind. This vapour must go somewhere, and it certainly does not fall in any place near the region where it is drawn up. See the beautiful provision of Nature to supply with fertilising moisture the many districts of the earth! This damp vapour, of which we shall by-and-by have a specimen, rises into the upper regions of the air, and is there wafted steadily on till it reaches the northern portion of the globe. It is raised by the powerful rays of the sun during the southern summer, and with it a considerable amount of heat is carried off which remains latent. When it reaches the far colder atmosphere of the north, it is formed into clouds, and condensed, and then precipitated in rain. In the southern hemisphere there is, as you know, a larger proportion of sea than in that of the north; and thus it serves as a reservoir to supply those spots which would otherwise be arid deserts, with an abundant supply of the chief necessary of life. The whole of nature is full of similar beautiful arrangements for making the globe a convenient habitation for man, clearly to be perceived if men would but open their eyes to behold them.”