Geology and Mineralogy. 243 



King ; and finally, with more special mention of results and of 

 workers, the existing IT. S. Geological Survey, organized by- 

 Clarence King in 1879, and placed the following year under the 

 directorship of Major Powell, and from the first carried forward 

 over all parts of the continent " even the most inhospitable," 

 with an energy that "recalls the heroism of an army attacking 

 obstacles the most arduous and most inaccessible." 



2. Geology of the Tonga or Friendly Islands. — A valuable 

 paper on these islands of the South Pacific, by J. J. Lister, is 

 published in the Quarterly Journal of the Geological Society, 

 vol. xlvii, p. 590, June, 1891. The region of the group — whose 

 length is about 250 English miles — is remarkable for the great 

 diversity of level in the islands and in the ocean adjoining. 



On the west side, along a course nearly N.N.E., the islands, 

 from Amargura in 18° S. and 174° 25' W. to Honga Tonga in 

 20° 35' S. and 175° 25' W. are volcanic, and the heights occur of 

 1890 feet in Lette I., 151 in Metis I, 3030 in Kao, 1890 in Tofua, 

 and 300 feet in Honga Tonga. 



Just east (30 to 40 miles), along an irregularly parallel line, 

 occur: Vavau at the north, in 18° 35' S. and 174° W., with 

 nothing but coral reef limestone in sight, and having on the IS". 

 and N.E. sides the limestone rock in cliffs 300 to 500 feet high ; 

 the Hapai Group, consisting mostly of coral reef rock, 20 to 100 

 feet high; the Nomuka Islands, consisting of tufa, having coral 

 reefs to eastward 30 to 60 feet high ; at the south end, Tongatabii,* 

 in 175° W. and 21° 10' S., a coral island with a shallow lagoon, 

 but raised 60 feet above the sea-level on the southeast side. 



About 10 miles to the southeast of Tongatabu is Eua, a vol- 

 canic island over 1000 feet high at two points, but encased in 

 coral-reef to a height at one point, by estimate, of 300 feet, and 

 another of 500 feet, and having cliffs of the limestone " some 200 

 feet high " along the eastern and western sides. 



Mr. Lister's paper which is illustrated by maps and sections, con- 

 tains other facts of geological importance. He refers to the great 

 depths of the sea to the southeastward and eastward of the 

 group; to the southeastward 230 miles, in 175° 08' W. and 24° 

 37' S., 4428 fathoms, and in 175° 07' W. and 24° 49' S., 4295 

 fathoms; to the eastward of Vavau, 150 miles, in 172° 14^' and 

 17° 04' S., 4530 fathoms. On the bathymetric map in this 

 Journal, vol. xxxvii, and also page 420, and vol. xxxix, p. 412, 

 other soundings in the vicinity are given, but none have been 

 obtained on the direct line between the two deep depressions. 



The soundings make the total height of the summit of Kao 

 above the deepest point in the ocean to eastward a little over 

 30,000 feet. Such depressions are not a result of loading the 

 crust by deposition. The range of facts here reviewed indicate 

 that some profounder method of causing change of level has 

 been at work. j. d. d. 



* The accent is on the first and last syllables —the latter half being the Polyne- 

 sian word tabu. 



