As has been said, if I mistake not by Daubeny, John Phillips, by Herschell, and by myself, the function of the Earthquake and the Volcano is not destructive but, preservative. But we now see that: that the preservative scope of this function, as respects our earth, is far wider than what has been previously attributed to it. The Volcano does not merely throw up new fertile soil, and tend, in some small degree, to restore to the dry land the waste for ever going on by rain and sea; it fulfils a far weightier and more imperative task; it—by a mechanism the power of which is exactly balanced to the variable calls demanded of it, and which working almost imperceptibly, although in a manner however terrible its surface-action may at times appear to us little men[G]—prevents at longer intervals such sudden and unlooked-for paroxysms in the mass of our subsiding earth's shell as would be attended with wide-spread destruction to all that it inhabit.
To the popular mind, Volcanoes and Earthquakes are only isolated items of curiosity amongst "the wonders of the world:" few geologists even appear to realise how great and important are the relations of Vulcanicity to their science, viewed as a whole. Yet of Vulcanicity it is not too much to say, that in proportion as its nature and doctrines come to be known and understood as parts of the Cosmos, the nearer will it be seen to lie at the basis of all Physical Geology.
[A] For a fuller account of the literature and history of advancement of human knowledge as to Earthquakes, here merely glanced at, I must refer to my First Report on the Facts of Earthquakes, "Reports, British Association, 1850," and to the works of Daubeny, Lyell, Phillips and others, its complete history remaining yet to be written.
[B] Yet how indistinctly formed were Young's ideas, and indistinct in the same direction as those of Humboldt, becomes evident by a single sentence: "When the agitation produced by an Earthquake extends further than there is any reason to suspect a subterraneous communication, it is probably propagated through the earth nearly in the same manner as a noise is conveyed through the air."—Lectures, Nat. Phil., Vol. I.
[C] The Right Rev. Charles Graves, F.R.S., etc., then Fellow of Trinity College, Pres. R. I. Acad., and now Bishop of Limerick, on presentation of the Academy's Cunningham Medal.
[D] In this Report, though I have never before referred to it, and do so now with reluctance, I have always felt that the Author did me some injustice. The only reference made to my labours, published the preceding year only, is in the following words: "Many persons have regarded these phenomena (viz., Earthquakes) as due in a great measure to vibrations ... and the subject has lately been brought under our notice, in a Memoir by Mr. Mallet, 'On the Dynamics of Earthquakes,' in which he has treated it in a more determinate manner, and in more detail, than any preceding writer" (p. 74). If that Paper of mine be collated with this Report, it will be, I believe, found that, as respects the earthquake part, the latter tint parades, in a mathematical dress, some portions of the general theory of earthquake movements, previously published by me as above stated. So, also, in the chapter (p. 90) referring to Seismometry, and the important uses to Geology that might be (and since have been, to some extent) made of it, no mention is made of those instruments previously proposed by me, nor of my anticipation of their important uses. This is but too mortifyingly suggestive of the—
"Pereant qui mea ante mihi dixerunt."
Having left this unnoticed for so many years, and during which the Author has preceded me to that bourne where our errors to each other must be forgotten, I should certainly not have now trespassed on the good rule, De mortuis nil nisi bonum, had I not observed very recently one amongst other results probably attributable to it. In Professor Phillips's "Vesuvius," if any one will refer to the passage beginning "The mechanism of earthquake movement has been investigated by competent hands. The late eminent mathematician, Mr. Hopkins, explained these tremors in the solid earth by the general theory of vibratory motion," etc. (pages 257-259)—I think he must, in the absence of collateral information, conclude that, not I, but Mr. Hopkins, was the discoverer of the Theory of Earthquakes as explained by the general theory of vibratory motion.
Probably my friend, Professor Phillips, had not recently referred to those Memoirs and Reports of twenty-four years back, and I am thoroughly convinced that, if he has here perpetuated an injustice, he has done so unintentionally and unwittingly.