VULCANOLOGY AND SEISMOLOGY. 303 



theoretical methods and calculations employed in making deductions 

 from earthquake observations. For this Prof. John Milne received the 

 first prize of loO guilders and a diploma. He also received honorablo 

 mention for an essay on the application of theoretical seismology to the 

 art of housebuilding. (Nature xxxiv, 154.) 



The Japanese Transactions of the Seismological Society of Japan 

 have reached Yol. iii, which contains i^apers on "Earth Tremors," 

 by Milne; on the " Earthquake of October 15, 1884," by Sekiya ; and on 

 "Air Waves and Sea Waves," by Wada. The English Transactions of 

 this active society have completed Vol. ix, the contents of which are 

 referred to in their appropriate places in this summary. • 



SEISMOMETRY. 



Early in the year Professor Milne read before the Seismological So- 

 ciety a paper on a seismic survey made in Tokio in 18S4-'85. It is a 

 fuller account of experiments briefly described in his "Fifth Eeport" 

 to the British association, 1885. A number of similar seismographs 

 were installed at different points on the grounds of the Imperial Col- 

 lege of Engineering, one being at the bottooi of a jiit 10 feet deep, and 

 another in a house supported on cast-iron balls. The instruments were 

 connected and simultaneously put in operation by electricity. During 

 the year of observation fifty earthquakes occurred, whose automatic 

 records were studied. A map of the grounds is given and copies of 

 some of the record diagrams. In general the results differed very 

 sensibly at the various stations, the motion being usually greatest on 

 the low grounds. The greatest amplitude marked at any station was 

 2.5 millimeters, while the same earthquake at another station gave 

 only 0.05 millimeter. The greatest " maximum velocity" recorded is 19 

 millimeters per second. The greatest acceleration was 300 millimeters, 

 or about 1 foot per second. In the house resting on shot the least mo- 

 tion was found when the shot used were small, about a quarter of an 

 inch in diameter. 



Experiments have been made with delicate instruments by MM. 

 Fouque and Levy on the velocity of propagation of vibrations in the 

 soil, the vibrations being produced by dynamite and by the blow of a 

 pile-driver. Some of their conclusions are of interest. (1) The vibra- 

 tions caused by charges of dynamite or powder (up to 12 kilograms of 

 dynamite) are, at the same distance, more feeble than those produced 

 by a hammer of 100 tons falling from a height of 5 meters. (2) When 

 the point of disturbance and the basin of mercury are both at the sur- 

 face the vibrations are multiplied, showing several maxima and minima, 

 and at a distance of 1,200 meters lasted 10 seconds. On the contrary, 

 when the origin of the disturbance is below the surface, as in a mine, a 

 single blow gives rise to a single shock of short duration, even when 

 observed at a great distance ; and the result is the same whether the mer- 

 cury basin be in the mine or on the surface. (Compt. Rend., cii, 1290.) 



