Page:Popular Science Monthly Volume 77.djvu/441

Rh Fiji, or we may have a submerged crater the volcanic rim of which may erode away to beneath sea-level, thus giving a foundation for a ring-shaped coral reef.

Unfortunately the very multitude of Alexander Agassiz's observations, and the somewhat confused style of his writing, renders him difficult to follow. Had he enjoyed greater experience as a lecturer he might have become a clearer writer, for he constantly assumed that his readers were as familiar with the subject as himself, and that a few words would make his meaning as clear to them as to him.

It is to be regretted that of the three great writers upon coral reefs Darwin saw only one atoll, Dana sailed past many but was permitted to land upon few, for the islands were then inhabited by dangerous cannibals, and Agassiz was compelled to cover such a vast field that certain of his conclusions, as he states himself, are still tentative; for the solution of some of the questions presented by these problems demands a more intensive and prolonged study than he was able to devote to them.

While in the Hawaiian Islands in 1885 he found that the coral reefs have repeatedly been buried under lava floes, and that the corals have again grown over the submerged lava. The reefs have nowhere been elevated more than 25 feet above sea-level, but the coral sands and shell fragments have been blown upward along the mountain slopes and have formed limestone dunes which the rains have cemented into solid rock. These wind-blown limestone ledges may be found 700 feet or more above the level of the sea.

In 1890 he published a paper showing that reef corals may become two and one half inches thick in less than seven years, his observations being based upon a study of corals that had grown upon the Havana-Key West cable.

In 1887 Alexander Agassiz was invited by the U. S. Fish Commission to assume the scientific direction of an expedition of the steamship Albatross between Panama and the Galapagos Islands, but he was unable to accept until 1891, when from February until May he cruised with the Albatross from Panama to Point Mola, thence to Cocos, Malpelo and Galapagos Islands, and from Acapulco to the Gulf of California, making 84 deep-sea trawl hauls, soundings and temperature observations, and in five more stations using the surface and sub-marine nets.

A significant feature of this expedition was due to the invention by Lieutenant Commander Z. L. Tanner, U.S.N., of a self-closing net which enabled one to obtain marine animals at any stratum of depth, and thus to determine the range in depth of marine creatures. The use of this excellent net led Alexander Agassiz to conclude that the floating life of the surface of the sea does not sink to a depth greater