ON THE PACTS OP EARTHQUAKE PHENOMENA. 317 



experiments in the closet to ascertain the moduli of elasticity of various rocks 

 or other mineral masses cannot but be of great interest and value to 

 science, they will be of less direct importance to seismology than was at 

 first anticipated, and that no determinations of the transit rate of earthquake 

 waves can be made in a trustworthy manner, except — 1st, by multiplying ex- 

 periments in various rocks or discontinuous formations of different degrees 

 of heterogeneity and homogeneity, by the method described in the preceding 

 pages, by that of MM. Wertheim and Breguet, which is applicable in some 

 instances with great advantage and convenience, or by some other which may 

 be devised ; and 2nd, by actual instrumental determinations of the rate of 

 earthquake-waves as they occur in nature : this can only be done by self-re- 

 gistering instruments such as that at present attempted to be constructed. 



It is scarcely necessary further to revert to the deep interest that attaches 

 to such researches, affording, as they do, the most direct and likely means of 

 acquiring some information as to the — 



1. Depth below the surface of the great seats of volcanic action, and their 

 identity or not, in position and nature, with the great forces of elevation. 



2. Depth of the solid crust of the earth. 



3. Nature of the great oceanic beds. 



To the following gentlemen my especial thanks are due for aid rendered 

 to me and to my son William, who assisted throughout in these experiments. 

 To Sir John F. Burgoyne, K.C.B., the Master- General, and the respective 

 Officers of Ordnance ; to Dr. Robinson, for the kindest interest and encou- 

 ragement and much valuable suggestion and information ; to Professor 

 Wheatstone, for the use of his chronograph and communication of his expe- 

 rience as to the best modes of bringing it into use ; to the Directors of the 

 Dublin and Kingstown Railway, for the use of the telegraph wires at Dalkey ; 

 and their officer Mr. Bergin, for the loan of his galvanic batteries ; to Pro- 

 fessor Downing, for aid in the admeasurement of the first base line ; and to 

 Barry D. Gibbons, Esq., C.E. and M. B. Mullins, Esq., Contractor of Kings- 

 town Harbour, for assistance in the operations upon the granite ; with others, 

 whose assistance, if less defined, was highly important. 



I now proceed to the EARTHQUAKE CATALOGUE, and the re- 

 sults obtained by its discussion. 



Of the Construction of the Catalogue. 



Former partial catalogues, more especially those of Von Hoff, Cotte, 

 Hoffman, Merian, and Perrey, have formed the basis of the present, as I be- 

 lieve first attempt, to complete a catalogue that shall embrace all recorded 

 earthquakes. By the first and last of the preceding authors our labours have 

 been most lightened. In Von Hoff's Catalogue (Gesch. d. Verand. &c. vol. iii.) 

 a total break occurs from the year 1806 to 1820 inclusive, and it ends with 1832. 

 M. Perrey's numerous and valuable local catalogues are scattered through va- 

 rious foreign journals ; he has latterly produced and still continues to publish 

 a current annual catalogue, for which he is anxious to receive contributions 

 from observers of intelligence situated in all parts of the world, addressed to 

 him at Dijon. Besides the above and some minor catalogues, our work has 

 been compiled from multitudes of scattered sources, collected in foreign and in 

 British libraries, the accessions from which have at least amounted to as much 

 as from all prior catalogues. 



Notwithstanding much labour and time, it is not for a moment to be as- 

 sumed that the present catalogue is complete, that it embraces all known 

 records of earthquakes ; such a work would probably be impracticable ; in 



