316 



REPORT 1851. 



Table No. 8. 



Probable Transit Rates of Earthquake Waves, as observed and calculated, 

 from various authorities. 



Occasion and Place. 



Approximate 

 rate in 

 feet per 

 second. 



Formation constituting range on 

 surface so far as known or 

 conjectured. 



Authority. 



Rev. John Mitchell's guesses, from 

 the Lisbon earthquakes 



Von Humboldt's ditto, from South 

 American 



j 1760 I 



fromnCO [ 

 to 2464 1 



Sea-bottom, probably on slates, 

 secondary and crystalline rocks 



From observations in various 

 South American rocks, in great 

 part volcanic 



I Mi 



Lisbon Earthquake of 1761. 

 Lisbon to Corunna 



Lisbon to Cork 



Lisbon to Santa Cruz 



Antilles. 

 Pointe a Pitre to Cayenne (doubtful) 



India. 

 Cutch to Calcutta (1819) 



/ndza.— Nepaul and Basin of the 

 Ganges (1834). 



Rungpur to Arrah 



Monghyr to Gorackpur 



Rungpur to Monghyr 



Rungpur to Calcutta 



1994 

 5228 

 3261 



6586 

 1173 



2314 



3520 



990 



1210 



Transition, carboniferous and 

 granitoid 



Transition, carboniferous, cry 

 stalline slates and granitoid, 

 probably, under the sea-bottom 



The same with many alter- 

 nations 



Ships Rambler and Millwood at 

 Sea (1851). 



Between lat. 16° 30' N.long., 54° 

 30' W., and lat. 23° 30' N., long. 

 5S°0'W 



Probably volcanic rocks under ' 

 sea- bottom 



Alluvial, secondary, granitoid, 

 and later igneous rocks 



Deep alluvia, with occasional 

 transition, carboniferous, gra- 

 nitoid, and later igneous rocks 



Sea-bottom resting on unknown 

 rock 



Mitchell. 

 Humboldt. 



1 Annual 

 J Register. 



} Annual 

 Register. 



1 Annual 

 J Register. 



Itier & Perrey, 

 Mem. Dijon. 



Royal 

 Asiat. Journ. 



Royal 

 " Asiat. Journ. 



Nautical 

 zine. 



It seems highly probable that future instrumental determinations of the 

 rates of natural earthquake-waves will show that — 



1. In cases where the line of movement of the wave is not far from vertical, 

 occurring in hard crystalline and very solid rock of one sort, and having an 

 origin at a considerable depth, the rate of wave transit will approximate nearly 

 to that of a normal wave due to the modulus of the formation, the rate of the 

 wave being also probably affected by the limits of the mass in which it moves. 



2. That in every superficial rock formation, as being all more or less 

 shattered and none homogeneous, and in any given extensive range several 

 different formations intervening, the rate of transit will be found probably 

 seldom or never to approach the preceding velocity. 



3. While in discontinuous media, such as sand, gravel, diluvial clays, mud, 

 &c., the rate of transit will be the slowest of all, although for reasons given 

 in the former Report, the destructive effects of the wave in such materials may 

 be greater than in any other. 



It follows, from the conclusions that we have so far arrived at, that while 



