PHYSIOGRAPHY OF THE HAWAIIAN ARCHIPELAGO.
The Hawaiian Archipelago, "the loveliest fleet of islands an chored in any ocean," is usually described as consisting of eight high inhabited islands with a N. W., S. E. trend. The nautical charts, however, show a dozen smaller low islands and shoals situ ated to the northwest of the more important part of the group, over which the authority of the territorial government is now ex tended. The archipelago extends over twenty-five degrees of longitude, or about i,800 miles. The following table presents their names, order, areas and extreme altitudes : The uninhabited islands have an area estimated at six square miles, making the total of 6,460.
These islands are partly those termed low and those high. The first may be swept by the ocean waves in times of storms or may be simply reefs or shoals. Their origin may have been the same as that of the high islands which are supposed to have been igneous protrusions from the bottom of the ocean. The low islands may be capped by coral growth which commenced ex istence after the igneous eruptions had ceased. This archipelago may be conveniently divided into first, the low islands and shoals, secondly the high islands below i,000 feet in altitude above the sea level, and third those that exceed i,000 feet above the sea with their satellites.
The depth of the ocean adjacent is put from i6,000 to i8,000 feet as determined by soundings. Adding to these figures the ele vations of the highest volcanoes on Hawaii, we have the evidence of the existence of volcanoes 30,000 feet high. If arranged on a line, the islands of this archipelago represent a row of conical peaks from t8,000 to 30,000 feet.
These cones must be very blunt, with a base of say two degrees upon each side, or four degrees for i6,000 feet altitude, which would represent an incline of about one hundred and fifteen feet to the mile. This corresponds with the existing visible slope of Mauna Loa. This slope is so gradual that one can hardly realize that the mountain is nearly 14,000 feet high, when viewed from a distance of thirty miles ; and the suggestion that the steep needles or islands might be overturned by earthquakes is surely un founded. These islands are not arranged upon a single line, and
the soundings prove that other cones are scattered indiscriminately about the archipelago which do not reach the surface of the water. The submarine area adjacent to these islands must be very exten sive, so much so as to suggest the existence of Tertiary strata through which the volcanoes have eaten their way.
Many authors believe that Ocean islands represent the first of these volcanoes to commence eruption, followed by the rest of the first group and by the higher islands successively. Kilauea is the last because that is now an active volcano, and should another grand volcanic display be manifested in the future, it will be located to the southeast of Hawaii. This theory is probably cor rect in the general way ; supplementary details may be suggested by the descriptions in Oahu, Maui and Hawaii.
The charts published by the Hydrographic Office of the Navy Department of the most remote low islands of the Hawaiian Archipelago were prepared from observations made by the officers of the U. S. steamer Lackawanna in The others have been explored by European navigators. This series is extensively used by mariners in the mid-Pacific, and the sailing directions are being constantly perfected, chiefly by the Navy Department of the United States.
In 1899 the U. S. S. Nero, under the direction of Lieut. Com mander H. M. Hodges, was fitted up with the necessary apparatus to take soundings, observe the temperatures and the character of the sea bottom between Honolulu and the Philippines by the way of Guam, and this was for the determination of the proper route for a telegraphic cable. I will mention the principal matters of interest ascertained along this line between Honolulu and Mid way, where a cable office has been established.