290 REPORT— 1893. 



4. ' On tlie Observation of Earth-tips and Earth Tremors,' ' Nature,' vol. xxxii. 



1885, pp. 259-262. 



5. ' Earth Tremors in Central Japan,' ' Japan Seism. Soc. Trans.,' vol. xi. 



1887, pp. 1-78. 



6. 'Earth Tremors in Central Japan," Japan Seism. Soc. Trans.,' vol. xiii. pt. 1, 



1888, pp. 7-19. 



7. ' Earth Tremors and the Wind,' ' Roy. Met. Soc. Journ.,' vol. xiv. 1888, 



pp. 64-72. 



8. ' Earth Pulsations in relation to certain Natural Phenomena and Physi- 



cal Investigations,' ' Japan Seism. Journ.,' vol. i. 1893, pp. 87-112. 



9. ' On Earth Pulsations and Mine Gas,' 'Fed. Inst. Mining Eng. Trans.,' vol. v. 



1893, pp. 20.3-219. 

 10. ' Reports on the Seismological Phenomena of Japan,' ' Brit. Assoc. Rep.,' 

 1S81, p. 202 ; 1883, pp. 211, 212 ; 1884, pp. 249-251 ; 1885, pp. 374-378 ; 

 1887, pp. 219-226 ; 1888, pp. 433-435 ; 1892, pp. 107-113. 



Seismic Oscillations of the Oround-water Surface. — Some interesting 

 observations have recently been made on this subject by Professor 

 Franklin H. King in vsrells in the "Wisconsin agricultural experiment 

 station farm.* The instrument employed consists of a copper float con- 

 nected with the end of the short arm of a lever. The longer arm is three 

 times as long as the other, and at the end carries a pen which traces the 

 magnified fluctuations of the water-level on a moving sheet of paper. The 

 recording apparatus is placed on a slab over the top of the well. 



The well in which these observations were made is 40 feet deep, and 

 is tubed with 6-inch iron pipe down to the rock (sandstone), 37 feet below 

 the surface, the water having a mean depth of about 20 feet. At a 

 distance of 140 feet from the well there is a railway line. 



When the records from this well were examined, numerous sharp, 

 short period curves were found, which were at first supposed to be due to 

 accidental disturbances of the apparatus. But the fact that they were 

 always dependent from the main curve, indicating a rise of water in the 

 well, led to their closer examination and to their association with the 

 movement of trains past the well. ' The strongest rises in the level of 

 the water are produced by the heavily- loaded trains which move rather 

 slowly. A single engine has never been observed to leave a record, and 

 the rapidly moving passenger trains produce only a slight movement, or 

 none at all, which is recorded by the instrument.' The curve is produced 

 by ' a rapid but gradual rise of the water, which is followed by only a 

 slightly less rapid fall again to the normal level, there being nothing 

 oscillatory in character indicated by any of the tracings nor observable 

 to the eye when watching the pen while in motion. The downward move- 

 ment of the pen usually begins when the engine has passed the well by 

 four or five lengths, and when the pen is watched it may be seen to start 

 and to descend quite gradually, occupying some seconds in the descent.* 



The cause of these movements of the ground-water surface is not 

 quite clear. Possibly the earth, being depressed by the weight of the 

 train, and sinking into the ground-water, may displace it laterally, and 

 thus cause it to rise under the surrounding area; or the compression of 

 the zone of capillarily saturated soil lying just above the ground- water 

 surface, or its frequent recoils from the shock imparted by the moving 

 train, may force some of the capillaiy water out of the soil, and thus 

 raise the mean level of the ground- water. 



' ' Observations and Experiments on the Fluctuations in the Level and Rate of 

 Movement of Ground-water, &c.' United States Weather Bureau, Bull. No. 5, pp. 

 67-69. See also a paper by Mr. Isaac Roberts, F.R.S., in the Brit. Assoc. Hep., 1883, 

 p. 405. 



