200 



SCIENCE 



[X. S. Vol. XXXII. No. 815 



servations, extending over a period of nearly 

 seven years, of the deformation of the earth 

 under the influence of the moon. The instru- 

 ment (or instruments, for two were set up) 

 used was a horizontal pendulum, in short a 

 seismograph, placed in a well some eighty 

 feet deep to eliminate the heat effect of the 

 sun. As the theoretical displacement of a 

 pendulum through the attraction of the moon 

 is a definite quantity, readily computed for 

 an absolutely rigid earth, the actual displace- 

 ment gives a measure of the yielding of the 

 earth itself, i. e., of the degree of rigidity. 

 Hecker's observations confirmed previous de- 

 terminations made however by different 

 methods, that the rigidity of the earth is 

 somewhat greater than that of steel. The 

 tide of the solid earth is from four to six 

 inches. An interesting point brought out 

 too was, that there is very little lag in this 

 earth tide, i. e., that " high earth " corre- 

 sponds to the transit of the moon for any 

 place. 



Another interesting paper was that of 

 Prince Galitzin on the determination of the 

 azimuth or direction of the epicenter from 

 the comparison of the corresponding ampli- 

 tudes of two horizontal pendulums at a single 

 station, one mounted in the N.-S., the other 

 in the E.-W. direction. He showed the inter- 

 agreement of his deduced azimuth for a dozen 

 known earthquake centers with the theoret- 

 ically computed one. 



The method of obtaining the distance to an 

 epicenter has of course for some time been 

 readily available from the time interval be- 

 tween the diilerent phases of an earthquake 

 record; for instance, between the arrival of 

 the first longitudinal waves and the first 

 transverse waves; or the first long waves. 



Of any individual question or subject dis- 

 cussed, the one on microseisms elicited the 

 most interest. These microseisms or earth 

 tremors have been observed practically over 

 the whole earth, and are quite distinct from 

 pulsations produced by earthquakes. They 

 last for hours and days, and have a period of 

 about five seconds. The actual amplitude 

 (half range) of the earth particles reaches five 



microns, or one two-hundredth of a milli- 

 meter. 



The writer communicated the results of his 

 investigation extending over several years, 

 which shows that they are due in the first in- 

 stance to areas of low barometer, surrounded 

 by steep gradients, and in the second place, 

 that such an area of low barometer is far 

 more effective in producing microseisms 

 when it is resting or passing over water, that 

 is, the ocean. Experience shows that for the 

 Atlantic coast the microseisms appear more 

 strongly after the area of low has passed the 

 recording station and reached the ocean. Per 

 contra, in Europe the reverse should obtain, 

 as in general atmospheric movement between 

 Canada and Europe is easterly, that is, the 

 microseisms there should show themselves 

 hefore the low reaches the land. 



A special committee was appointed to 

 further investigate this interesting problem, 

 and to that end it is probable that one or 

 more instruments, especially designed for the 

 purpose, will be set up on the seashore to 

 record the pulsations of the water. 



The present mareographs or tide-gauges 

 are not adapted for that purpose, the time- 

 scale being far too small, for one must be 

 able to read at least to five seconds of time on 

 the record. A thousand Marks, or $250, was 

 placed at the disposal of this committee. 



The conference was successful in every re- 

 spect. The members were all housed in the 

 same hotel, and this enhanced the opportunity 

 of " heart to heart " talks which are really 

 the most valuable assets that meetings of 

 scientific men offer. 



Otto Klotz 



THE GRADUATE SCHOOL OF AGRICULTURE 

 The fourth session of the Graduate School 

 of Agriculture, which has been in progress 

 for the past four weeks at the Iowa State Col- 

 lege at Ames, was brought to a close July 29. 

 The session was entirely successful from 

 the standpoint of numbers enrolled and char- 

 acter of the lectures given. The total enroll- 

 ment was 207, in this number 39 states, the 



