Sometimes the are in groups, or clusters, like the cluster at the Sandwich Islands, or in the Friendly Islands, or in New Zealand.

And if we look in the Atlantic, we shall see four clusters: one in poor half- destroyed Iceland, in the far north, one in the Azores, one in the Canaries, and one in the Cape de Verds.

And there is one dot in those Canaries which we must not overlook, for it is no other than the famous Peak of Teneriffe, a volcano which is hardly burnt out yet, and may burn up again any day, standing up out of the sea more than 12,000 feet high still, and once it must have been double that height.

Some think that it is perhaps the true Mount Atlas, which the old Greeks named when first they ventured out of the Straits of Gibraltar down the coast of Africa, and saw the great peak far to the westward, with the clouds cutting off its top; and said that it was a mighty giant, the brother of the Evening Star, who held up the sky upon his shoulders, in the midst of the Fortunate Islands, the gardens of the daughter of the Evening Star, full of strange golden fruits; and that Perseus had turned him into stone, when he passed him with the Gorgon's Head.
But you will see, too, that most of these red and black dots run in crooked lines; and that many of the clusters run in lines likewise.
Look at one line: by far the largest on the earth.

You will learn a good deal of geography from it.
The red dots begin at a place called the Terribles, on the east side of the Bay of Bengal.