MOVEMENTS AXD DEFORMATIONS OF THE EARTH'S BODY. 537 



by five or six miles."' In still another case (1885) the repairing vessel 

 found a ^' clifTerence of 1500 feet between the bow and stem soundings.'' 

 These records point to sea-bottom faulting on a large scale. 



It is probably no nearer the truth to say that changes of level result 

 from earthquakes than to say that earthquakes result from changes 

 of level. The two classes of phenomena are probably to be referred to 

 a common cause. * 



SLOW :\IASSIVE MOVEMEXTS. 



It is a far cry from tlie intense and inconceivably rapid oscillations 

 of the earthquake, to the excessively slow subsidences of continents, 

 or even the slow T\Tinkling of mountain folds. Xot infrequently rivers 



wear doAvn their channels across a mountain range as fast as it rises 

 athwart them. The movements of continents are even more deliber- 

 ate. But. far apart as these contrasted movements are. in rate and 

 method, they are associated in ultimate causation, and the earthquake 

 shock is often merely an incident in the formation of a mountain range 

 or in the subsidence of a continent. 



The great movements are usually classed (1) as continent-making 

 (epeirogenic) and (2) mountain-making (orogenic). They may also be 

 classed as (1) vertical movements and (2) horizontal movements, and 

 dynamically, as (1) thrust movements and (2) stretching movements. 

 It is to be understood that these distinctions are little more than analyt- 

 ical ccnA'enienceS; for continental movements are often at the same time 

 mountain-making movements: A^ertical moA-ements are usually involved 

 in horizontal movements, and stretching usually takes part in the proc- 

 esses in which thrust predominates, and vice versa. But where one 

 phase greatly preponderates, it may conA'eniently give name to the 

 whole. 



^ The lit-erature of seismology is very extensive. Some of the more general treatises 

 are the following: Mallet, Brit. Assoc, 1S47, Part II, p. 30; 1850, p. 1; 1851, p. 272; 

 1852, p. 1; 1858, p. 1; 1861, p. 201; and The Great Xeapolitan Earthquake of 1857, 

 2 Vols., 1862; A Perrey, Mem. Couronn. BmxeUes, XVIII (1844), Compt€s Rendus, 

 LIT, p. 146; R. Falb. Gnmdziige einer Theorie der Erdbeben tmd Vulkanenausbruche, 

 Graz, 1871, and Gedanken und Studien iiber den Yulkanismus, et-c., 1874; Pfafif, 

 AUgemeine Geologie als exacte Wissensehaft, Leipzig, 1873, p. 224; Schmidt, Studien 

 iiber Erdbeben, 2d ed., 1879, and Studien iiber Vulkane imd Erdbeben, 1881; Dieff en- 

 bach, Xeues Jahrb., 1872, p. 155; M. S. di Rossi, La Met^orologia Endogena, 2 Vols., 

 1879 and 1882; J. Milne, Earthquakes and other Earth-movements (contains a bibli- 

 ography), 4th ed., 1898; Seismology, ibid., 1898; Button, Earthquakes, 1904. 



Records of earthquakes have been preserved more or less fully in several countries, 

 especially in recent years. A few of the more accessible publications where these 



