250 Ilobbs — Features Formed at the Time of 'Earthquakes. 



thus produced is that they have a composition essentially dif- 

 ferent from that of the layers of soil underlying their margins, 



and that the materials are 

 derived from a .lower 

 horizon (see extract from 

 Yeatch above). The re- 

 port of the Naples Acad- 

 emy of Science upon the 

 great earthquake of Ca- 

 labria (1783) states that 

 some plains, like that of 

 Rosarno, were covered 

 with circular hollows 

 generally filled with sand 

 but sometimes with a con- 

 cave surface. At other 

 times, the surface was 



Fig. 2. Funnel-shaped pipe of sand formed 

 during earthquakes of Calabria in 1783 (after 

 Lyell). 



convex. Upon digging down in them it was found that they 

 were funnel-shaped pipes, and that the moist, loose, micace- 

 ous sand in the center marked the tube up which the water 

 had spouted (see fig. 2). At other places in the same district, 

 cones of sand were built up, and the localization of cones and 

 funnels upon fissure lines was recognized.* 



According to Yeatch and Fenneman, the G-ulf mounds differ 

 in composition from the material of the surrounding plain, and 

 they appear, further, to be often pitted at their summits. 

 Attention should therefore be directed more particularly to- 

 the composition of the mounds, taking account also of their 

 less common ingredients, and their relation to underlying 

 formations should be discussed. Apparently also there is a 

 possibility of determining the underground structure of such 

 mounds where they have been dissected. Especial interest 

 attaches, in this connection, to the sandstone pipes which 

 occur in the Carboniferous limestone of the eastern coast of 

 Anglesey, for which as yet no explanation has been offered. 

 The surface of the limestone is here pierced by a large num- 

 ber of circular pits opening out in trumpet form and from 1 

 to 7 feet in diameter. Each can be seen to be, or to have 

 been, filled with a plug of fine white sandstone, descending 

 into the limestone at right angles to its bedding.f 



"These plugs can be seen in various stages of denudation. 

 Some have been worn flush with the surrounding limestone, and 

 some of the smaller ones have been excavated so as to leave an 

 almost empty pit or pothole with a little sandy matter in the 



* Lyell, Principles of Geology, vol. ii, pp. 127-128. 



f Edward Greenly, On sandstone pipes in the Carboniferous limestone at 

 Dwlban Point, East Anglesey, Geol. Mag., Dec. IV, vol. vii, pp. 20-24, 1900. 



