97 



proposed to experiment upon the actual transit velocity of artificial 

 shocks, obtained by the explosion of gunpowder ; and aided by the 

 funds of the British Association, he in 1849-50 completed a train of 

 experiments by which he determined the transit wave-time of shock 

 for wet sand as the lowest limit, and for solid granite as the highest 

 amongst known cosmical media. The results, received at first with 

 much surprise, in consequence of the low velocities of transit found, 

 fully coincided with the author's theoretic views of 1846, and have 

 since been amply confirmed, and shown to be accordant with the 

 low velocities of natural shocks, as measured by Schmidt, Noggerath, 

 Mr. R. Mallet, and others. These experiments form the su.bject of his 

 second British Association report of 1851. In his first report, Mr. R. 

 Mallet had pointed out the importance of collecting into one great 

 catalogue, and fully discussing in relation to space and time, &c,, all 

 recorded earthquakes, with a view to evolve any secular laws, if such 

 existed. This laborious work he undertook with the efiicient help of his 

 eldest son, Dr. John "William Mallet, now Professor of Chemistry at the 

 University of Alabama; and between the years 1852 and 1858, they 

 completed together the British Association earthquake-catalogue, em- 

 bracing more than 6000 earthquakes, which form the subject of Mr. E. 

 Mallet's third and fourth British Association Reports. In the fourth 

 Report, he has discussed fully, and year by year, this mass of the statis- 

 tical facts of earthquakes, extending from the earliest times of history to 

 that date. The discussion of the facts evolved these amongst the most 

 striking results : — 1. That earthquakes are not truly secular phenomena 

 in time ; 2. That in modern times, when observations are best and most 

 numerous, although the whole train of phenomena over time is irregular 

 or non- secular, still there has been a decided preponderance of earth- 

 quakes occurring at intervals of from forty to fifty years, and that 

 these periods of maxima occur about the middle and the last decade of 

 each century. Mr. R. Mallet ventured to predict the recurrence of such a 

 group of earthquakes for the then coming years, 1850, 1860, or there- 

 abouts, and his prediction has been fully borne out. In the time- dis- 

 cussion, also, he showed that at present some part or other of the earth 

 is subject to at least one great earthquake every nine months. 3. In the 

 discussion as to distribution over the earth's surface, he pointed out for 

 the first time that earthquakes follow the great lines of mountain chains 

 and elevations, forming what he has denominated Seismic Bands, the 

 whole of which he has laid down upon the Mercator Seismographic map 

 of the world published by the British Association. The important and 

 pregnant relations that this great fact possesses with respect to our 

 future knowledge of volcanic action, were in some measure pointed out 

 in this Report : their important bearing cannot be in this respect over- 

 estimated. Between the period of publication of his first and second 

 British Association Reports, Mr. MaUet had, at the request of Sir John 

 Herschell, drawn up for the Admiralty Manual the article on earthquakes 

 and the methods of observing them, which he further improved in the 

 second edition of that work. This article has been translated into 



a. I. A. PEOC. — -VOL. VITI. O 



