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Rh enclosed by our coral reefs, which includes many hundreds of square miles.

"At the same time the air-supply through these pipes was so improved that the air in the pipes, by mechanical contrivances, was kept at a considerable pressure; and by means of valves and stopcocks, the act of breathing below water is performed as easily as in the atmosphere; and there is no need to come to the surface at all for purposes of respiration. The breathing apparatus is so constructed that every mouthpiece is connected with two sets of tubes, one of which receives and carries off the expired air, whilst the other supplies the fresh air to be breathed. In this way the awkward and unsightly gurgling of the expired air is prevented.

"The quality of the air for breathing has also been much improved by the admixture of a considerable proportion of oxygen with the air supplied, so that one respiration of this oxygenated air is only required where many respirations of non-oxygenated air would be needed.

"Thus you will find that it is not necessary to breathe oftener than once in four or five minutes when you are used to this mode of breathing.

"When we make excursions beyond the reef into the ocean we carry with us metal bottles of condensed oxygenated air, whereby we are enabled to remain many hours away from the air-pipes of the enclosed sea without inconvenience."

After this explanation, my Instructor proposed that I should accompany him on a short excursion below the water, in order that I might learn practically something of the mode of life and qualify myself for citizenship in this singular community.

So having taken off my clothes, I donned the