74THE POPULAR SCIENCE MONTHLY.
Architectural forms are not confined to the United States, nor to the American continent. The Giant's Causeway in Ireland is a familiar example of what they have in those parts, while under the Arabian sky the conditions resemble those in our arid Southwest,
Fig. 13.—Potholes in Intermittent Stream Course.
and there we find many fantastic rain carvings. Among these is the Sphinx of El Guerrah, carved by the rain-sculptor doubtless expressly to furnish answers to our "whys and wherefores" concerning this "wondrous architecture of the world."
Among the applications proposed for the newly liquefied gases is their use as aids in balloon navigation. An aëronaut having a few bottles of liquefied hydrogen or illuminating gas has the means of increasing the inflation of his balloon when necessary, and need not fear to waste a little gas when he wishes to diminish its levity. Prof. L. Errera, of Brussels, has suggested an apparatus which he calls the ceinture de natation, or natation belt, by which these objects can be conveniently accomplished.