GEOLOGY AND TOPOGRAPHY OF HAWAII. 105 



eaten away. This has progressed on Kauai until only the skilled geologists 

 can, in fancy, reconstruct its original dome-like outlines. 



Everywhere in the group, but especially on Kauai, is found excellent ex- 

 amples of one-time solid rocks which are passing into fertile soil through the 

 ordinary agencies of disintegration. In its earlier stages the new-formed soil 

 is open and porous like a gravel l)ed. In this condition it absorbs large quanti- 

 ties of moisture which rapidly seep away from the surface. The power of 

 lava soils to retain moisture varies with the mechanical state of the soil and 

 the amount of organic matter it contains. While the soil under cultivation on 

 Kauai is very fine, and for that reason retains water reasonably well, it is, in 

 most cases, very red in color, indicating that it has not been discolored by the 

 impregnation of vegetable acids, which in the forests and beds of valleys is 

 very liable to produce a characteristic black soil. 



Lava Soil. 



Generally speaking the soil on Kauai is everywhere good, but is light and 

 open, and requires much irrigation to make it fertile. The constant cultivation 

 of the land does much to improve the soil, and by the addition of carefully com- 

 pounded fertilizer and an abundant supply of water, enormous yields of sugar- 

 cane are secured. The growth of various crops affect the soil differently, as 

 they remove from it varying amounts of nitrogen, phosphoric acid, potash and 

 lime, which are the principal elements required by plants as food. Careful 

 experiments have shown that the amount of these elements removed varies 

 greatly even with -the different varieties of cane that are grown in the islands. 

 As a result, the care and proper fertilization of the soils of the group has been 

 the subject of much scientific .study. 



While the main central dome on Kauai is the most conspicuous natural fea- 

 ture, there are other important elevations. The Hoary Head range, which 

 extends down to the coast at Nawiliwili Bay, may be considered as part of the 

 backbone of the main mountains. The highest point on this ridge, Haupu, is 2030 

 feet ; but between this point and the central dome the ridge is much lower, 

 forming a pass for the Government road from Lawai to Lihue. 



Secondary Volcanic Cones. 



A number of secondary volcanic cones on Kauai are important in the general 

 topography of the island. The largest of these is Kilohana crater, which rises 

 from the level Lihue plain to a height of 1100 feet. The ejecta from this cone 

 has been thrown over tlie country-side roundabout within a radius of four 

 or five miles. In the neighborhood of Koloa are several small secondary vol- 

 canic cones within the radius of a few miles. The lava emitted by them was 

 black and of a peculiar ropey type. Along the sea-shore the sea water forces 

 its way under the surface and is often expelled through holes and open- 

 ings in the lava in this vicinty. At favorable seasons the water spouts high in 

 the air, forming great fountains termed "spouting horns." 



