248 CORALS AND CORAL LSLANDS. 



would probably be glad, after a short experience, to transfer it 

 to an island of larger dimensions, like Tahiti or Upolu, one 

 more varied in surface and productions ; that has its moun- 

 tains and precipices ; its gorges and open valleys ; leaping 

 torrents not less than surging billows; and forests spreading up 

 the dechvities, as well as groves of palms and corals by the 

 shores. 



The mineral alluded to above as the one mineral product 

 of atolls is calcite, or carbonate of lime, the material of the 

 coral rock; and this is the only kind on the great majority of 

 them. 



But on some of the smaller islands, in the drier equatorial 

 part of the ocean, there are, in addition to this, and the stones 

 brought by logs with the floating pumice, beds of gypsum 

 which have been made through the evaporation of sea-water 

 (which holds it in solution) in the gradually drying lagoon 

 basins ; and also large deposits of guano from the multitudes 

 of sea birds that occupy them. Such are Jarvis's, Baker's, 

 Rowland's, Maiden's, McKean's, Birnie's, Phoenix's, Ender- 

 bury's, and probably other islands in the dry central equatorial 

 Pacific. As these deposits are connected with the completion 

 of the coral island, and its accompanying reduction in size, and 

 illustrate one of the ways by which new minerals are added to 

 a destitute land, a few facts are here cited from an article in 

 the American Journal of Science, volume xxxiv. (1862), by 

 J. D. Hague, who resided for several months on the islands he 

 describes. 



Baker's Island is situated in lat. 0° 13' north, and long. 

 176° 22' west from Greenwich, and excepting Rowland's Is- 

 land, forty miles distant, is very remote from any other land. 

 It is about one mile long and two-thirds of a mile wide. The 

 surface is nearly level ; the highest point is twenty-two feet 

 above the level of the sea, showing some evidence of ele- 

 vation. 



Above the crown of the beach there is a sandy ridge which 

 encircles the guano deposit. This marginal ridge is about one 

 hundred feet wide on the lee side of the island, and is there 



