VTJLCANOLOGY AND SEISMOLOGY. 225 



face at all in a fluid condition, but have made their presence known 

 only by the altered condition of the overlying strata. 



On the theory that the motive power of volcanoes and earthquakes 

 is due to the vapor of water, it becomes necessary to explain how watei^ 

 can be suddenly brought in contact with the heated portions of the in- 

 terior of the earth in sufficient quantities to generate the explosive force 

 called for by the phenomena. To meet this difficulty S. Meunier {La 

 HCature, 1884. i, 379) assumes the crust to be thicker under the oceans 

 than under the land, and suggests that at the edges of the thicker parts, 

 that is, at the coast lines, masses may, by their own weight or by ex- 

 ternal strains, be cracked oft" from the solid crust, and may thus sud- 

 denly open a rapid communication between the included water of the 

 upper strata and the zone of dissociation by heat below. 



Under the name of Earth Pulsations, Prof. John Milne, of Tokio {Na. 

 ture, xxvni, 367), treats of movements of the soil which escape our notice 

 on account of the sloicness of their period. Showing that increase of 

 atmospheric pressure or the rise of the tide would so change the load 

 restiug on the surface as to make such motions probable, he cites the 

 increased activity of all microseismic api^aratus, and the increased flow 

 of gas from the pores of a coal seam attendant on the fall of the baro- 

 metric, column, as indications pointing in the direction of increased in- 

 ternal activity. Observation both in Italy and in Japan also shows 

 that the position of rest of a suspended pendulum is not invariable, the 

 variation from normal position being too great and too uniform to be 

 attributed to accidental causes. Other illustrations are drawn from 

 motions of the waters in English lakes at the time of the great Lisbon 

 earthquake, and from the motions not infrequently reported of the del- 

 icate levels of astronomical observatories, which have not been ac- 

 companied by sensible movements of the ground. The same writer also 

 discusses {Nature^ xxix, 290) the effect of earthquakes on buildings, 

 and the kind of buildings best adapted to escape injury therefrom. 

 Two plans are suggested: either to make the buildings strong and bind 

 them together with iron rods, so as to resist the strains which occur, 

 or to employ frame buildings comparable in structure to a wicker basket, 

 which may yield without being overthrown. The use of heavy brick 

 chimneys joined to wooden houses is especially condemned as danger- 

 ous. 



The authorities of the University of Tokio have instructed one of 

 their officers to devote himself wholly to the study of seismic phenom- 

 ena. The person thus appointed is Mr. Sekiya, the Japanese secre- 

 tary of the Seismological Society of Japan. 



In November, 1884, a conference to formulate plans for the systematic 

 observation and discussion of earthquakes in the United States was 

 held in the rooms of the Geological Survey at Washington. There were 

 present Messrs. J. W. Powell, 0. E. Button, and G. K. Gilbert, of the 

 Survey; C.Abbe and C. F. Marvin, of the Signal Service; H. M. Paul, of 

 S. Mis. 33 15 



