222 ANNUAL OF SCIENTIFIC DISCOVERY. 



rocks forms at intervals numerous islands, such as New Guinea, the 

 Carolines, the Ladrones, and others, until Japan, with its gold-bearing 

 rocks, is reached. Thus, in accordance with this theory, the basin of 

 the Pacific has on each side a continuous elevation of volcanic origin. 

 At intervals, on both sides, gold is now found, from Behring's Straits 

 to New Zealand ; and it is stated that at the " beach diggings" in Cal- 

 ifornia, a bluish sand, not unlike the pipe clay of Ballarat, is frequently 

 thrown up by the waves, and is found to contain gold in considerable 

 quantities. 



The conclusion arrived at by this reasoning is, that the great gold 

 fields of the world, as at present known, are included in the vast sys- 

 tem of volcanic rocks which surround the Pacific. This chain, 

 though broken here and there, is said to be traceable between Aus- 

 tralia and America, and to be easy of identification on both sides of 

 the ocean. Such a continuous and well-marked line of volcanic eleva- 

 tion has often received the attention of geologists. Humboldt's view, 

 which is the one generally accepted on the subject, is that the bed of 

 the Pacific attained its present depth at a comparatively late period ; 

 that its unbroken crust, forced down on the molten mass underneath, 

 caused a quantity of it to rush toward the line of fracture at the edges, 

 and that this disturbed matter found vent in the elevations which are 

 now connected with the gold fields of America and Australia. So far, 

 these considerations, as bearing on the science of geology, are highly 

 important ; but it has to be shown in what way gold is to be connected 

 with volcanic shocks in some places, and not in others. On this point 

 it is laid down by Sir Roderick Murchison, that the rocks which 

 are the most auriferous are of the Silurian age, and that a certain 

 geological zone only in the crust of the globe is auriferous at all. 

 Gold, he states, has never been found in any stratified formations com- 

 posed of secondary or tertiary deposits, but only in crystalline and 

 paleozoic rocks, or in the drift from those rocks. The most usual origi- 

 nal position of the metal is in quartzose vein-stones that traverse altered 

 Silurian slates, frequently near their junction with eruptive rocks. 

 Sometimes, however, it is partially diffused through the body of rocks 

 of igneous origin. From this it appears that volcanic eruptions, in 

 connection with Silurian rocks, are to be regarded as the origin of gold 

 formations. 



INTERESTING OBSERVATIONS ON EARTHQUAKES. 



It is well known to the scientific world that the subject of earth- 

 quake phenomena has for some years been made a specialty of investi- 

 gation by Mr. Robert Mallet, of England, and that several valuable re- 

 ports by this gentleman have been published by the British Association 

 and Royal Society, - - including a descriptive catalogue of seven thou- 

 sand earthquakes. When the intelligence of the great Neapolitan 

 earthquake of December, 1857, reached England, Mr. Mallet was de- 

 spatched, under the auspices of the Royal Society, to examine the dis- 

 trict affected, with a view of reporting on the phenomena in question. 

 This report has recently been laid before the public, and from it we 

 derive the following information : - 



The great Neapolitan earthquake of 1857 occurred in December, 

 thus adding another proof to the remarkable fact that earthquakes are 



