_Seismic energy in relation to historical time._—The distribution of seismic energy with regard to historical time is a subject which has been very carefully examined by Mallet, who collected together a catalogue of between six and seven thousand earthquakes, embraced between the periods B.C. 1606 and A.D. 1850. The earthquake of B.C. 1606 was on the occasion of the delivery of the law at Mount Sinai. Between B.C. 1604 and B.C. 1586 an earthquake probably occurred in Arabia, when Korah, Dathan, and Abiram were swallowed up. Another biblical record is that of B.C. 1566, when the walls of Jericho were overthrown. The earliest records from China is in B.C. 595; in Japan B.C. 285; in India A.D. 894. By using the number of earthquakes which have been recorded in each century as ordinates, Mallet constructed a curve, which apparently shows a continual increase in seismic energy, especially during recent times. This, Mallet remarks, contradicts all the analogies of the physics of the globe, and points out that the rapid increase in the number of earthquakes in latter years is chiefly due to the greater number of records which have been made, and the increase of the area of observation. No doubt many of the records made by the ancients have been lost. If we compare Mallet’s records, as he invites us to do, with the great outlines of human progress, we see that the two increase simultaneously, and we come to the conclusion that, taken as a whole, during the historical period the seismic activity of the world has been tolerably constant. These conclusions, based on the evidence at our command, are not to be confuted. If, however, instead of considering the seismic energy of the whole world, we consider the seismic energy of particular areas, it seems reasonable to expect that in certain instances sometimes a decrease and sometimes an increase in this energy might be discovered, especially, perhaps, in areas which are highly volcanic. In France we know that volcanic activity ceased at a period closely bordering on historical times, and it is not unlikely that seismic activity may have ceased at a corresponding time. In a country like Japan, it is possible that in one district seismic energy may be on the increase, whilst in another upon the decrease. In a country like England, it is probable that the seismic state is constant, and, whatever changes may be now occurring, they are taking place at so slow a rate that, even if our records of the historical period were complete, we could hardly be expected to find these changes sufficiently marked to be observable. For purposes of reference, and also for examining the present question, the table, page 240, has been compiled. The earthquakes given are chiefly those which have been recorded in histories as being more or less destructive.