706 THAPfSAdtlONS OP SE(JTlOlf Gt 



2. The Buratioil dnd Direction of Large Earthquake^ 

 By Dr. John Milne, F.R.S. 



Small earthquakes, as for example those which occur in this country, have a dura- 

 tion of a \'ew seconds near to their origin. At places 50 or 100 miles distaut they may 

 not be recordable. The duration, therefore, has varied between a few seconds and 

 zero. With many large earthquakes, however, this decay during transmission is 

 not appreciable, and duration near to their antipodes may be as great as it is near 

 to their orifrin. Duration as one of these disturbances travels, rather than decreas- 

 ing, at times appears to increase. The greatest duration is at about 90° distance 

 from an origin. That which occurs may be compared with what we observe after 

 a flask of water has been tilted. The contents oscillate like a pendulum, and any 

 one part of the fluid comes to rest about the same time as any other part. 



Another observation in connection with recent seismological observations is 

 that large earthquakes travel furthest in particular directions. I have taken 

 seventy-nine large disturbances with fairly well-known origins south of the Cau- 

 casus, north of India, and to the east or south of Japan. These e;irthquakes have 

 travelled further to the west than to the east, and there has only been a small 

 percentage of them that have found their way across the equator, to observatories 

 in the southern hemisphere. 



3. Report on the Excavation of Critical Sections in the Palceozoic Rocks 

 of Wales and the West of England. — See Reports, p. 231, 



4. The Soiifriere of St, Vincent : the Changes subsequent to the Eruption 

 of 1902. ByDv. Tempest Anderson, F.G.S. 



In 1002 the author visited St. Vincent, along with Dr. Flett, after the then 

 recent eruption. In 1907 ha revisited the island and examined the changes that 

 had taken place in the new deposits. 



In 1902 an incandescent avalanche descended into the valleys which occupy 

 the great tranverse depression across the island to the south of the Soufriere, and 

 in particular the Wallibu Valley was tilled for a great part of its course to a 

 depth of at least 100 feet, but less near its mouth. lu this deposit of red-hot 

 material the secondary pheuomena of re-excavation of the valley by the river, 

 the falls of hot ash, the steam explosions, aud the flows of boiling mud took 

 place, aud are described in the Report, Part I.^ In 1907 almost the whole of 

 tliis ash had been washed away, but a fragment remained in the shape of a terrace, 

 GO to 80 feet high, situated on the north side of the valley. The ash of which it 

 is formed is unstratititd, and contains very few ejected blocks or fragments of any 

 kind. The floor of the valley is all composed of water-sorted material, chiefly 

 gra^-el and coarse sand, but with a good many blocks as big as a man's head. 

 They represent ejected blocks and fragments of lava derived partly fi-om the ash 

 of 1902 and partly from older beds, the fine ash in each case having been washed 

 away. The surface of the gravel bed showed marks of quite recent running 

 water, aud during the last winter (1906-7) the river ran along the foot of the 

 north bank of the valley. When examined in March 1907, it ran along the 

 south side of the valley, and had already in those few months excavated a new 

 chaunel about 30 feet in depth. The stratification, as exposed in this new valley, 

 is very distinct, and the sorting by water, mentioned above, is very evident. 

 Further up the mountain the remains of the avalanche became more abundant in 

 the valley bottoms, and here they were also better preserved, so that traces of 

 the feathtr-pattern erosion, so noticeable in 1902, were still visible on the surface. 

 This was mainly due to the surface of these ash deposits, like those to be presently 



' Anderson and Flett, Phil. Trans., Series A, vol. 200, 1903 ; Anderson, 

 Geographical Journal, March 1903. 



