Some American Papers on Volcanoes. 477 



invasion of neighbouring territories, often on a truly grandiose 

 scale. 



9. Obstruction must be admitted as an additional factor in 

 determining the form of a folded range. There may be much truth 

 in the statement that several arcs of the Jura Mountains press 

 forward into the gap furnished by the subsidence of the Bhine " like 

 ■waves into a bay" (p. 526). 



10. Subsidence of a foredeep may, in many cases, have resulted 

 in part from the advance of the Cordillera. Or it may, on the other 

 hand, have helped to guide such advance. It is well to remember, 

 however, that at present the Andes are interpreted as furnishing an 

 illustration of back-folding turned eastwards, away from the long 

 belt of subsidence which seems to merit the designation foredeep 

 (p. 497). And also that central subsidences are claimed in well- 

 known cases, such as that of the Lombardy Plain, to which Salomon 

 ascribes the peripheral uprise of the tonalite of Adamello (p. 560). 



VI. — Some American Papkrs on Volcanoes. 



"The Present Condition of the Volcanoes of Southern Italy," by 

 U. S. Washington and A. L. Day. Bull. Geol. Soc. America, 

 vol. xxvi, pp. 375-88, 1915. 

 A study of the conditions prevailing at Vesuvius, Etna, and the 



.iEolian Islands in the summer of 1914. 



Puff Cones on Mount Usu," by Y. Oinouye. Journ. Geol., 



vol. xxiv, pp. 583-6, 1916. 

 The writer watched the eruption of July-August, 1910, and paid 

 several later visits. He describes puff-cones formed on mud-flows 

 from small craterlets : they developed about a year after the eruption 

 and are attributed to escape of gas. 



"An Unusual Form of Volcanic Ejecta," by W. E. Pratt. Journ. 

 Geol., vol. xxiv, pp. 450-5, 1916. 

 A description of concretion-like bodies found in the ash of the 

 Taal volcano, Luzon, in February, 1911. They appear to have 

 been formed by the coalescence of dust and water vapour in the 

 air, forming mud-balls, and may be described as " volcanic 

 hailstones". 



"Notes on the 1916 Eruption of Mauna Loa," by H. 0. Wood. 

 Journ. Geol., vol. xxv, pp. 322-36 and 467-88, 1917. 

 An amplification and correction of earlier observations, giving a 

 large amount of detail as to the special features of this eruption, 

 which included an outburst of fumes followed by lava-flows. 



"Activity of Mauna Loa, Hawaii, December-January," 1914-15, 

 by T. A. Jaggar, jun. Amer. Journ. Sci., vol. xl, pp. 621-39, 

 1915. 

 An amplification and revision of a previous paper, with a descrip- 

 tion of an ascent of Mauna Loa and the phenomena observed. It is 

 concluded that this outbreak was a preliminary summit-ebullition of 

 an eruptive period. 



