1897.] on Recent Advances in Seismology. 335 



quickly chilled to form a condenser, beneath which moisture collects 

 which otherwise wo aid have escaped to the atmosphere. For this 

 reason fields containing a certain number of stones are more fertile 

 than others where stones are absent. 



Another important question, bearing upon differential loading of 

 differently covered areas, depends upon the existence or non-existence 

 of a covering of vegetation. We know how much many plants pump 

 upwards to transpire during the day, but their action during the 

 night is to the writer quite unknown. Daring the night this trans- 

 piration may be small, but are they yet pumping to replace their 

 daylight loss ? 



An action of this sort, if it exists, only implies a transfer of load 

 from beneath to a higher level on the surface, but if on one part of 

 an area with a common water supply this goes on, whilst it does not 

 take place on another portion of the same, it would follow that the 

 former might be superficially altered in form. What is here stated 

 respecting the cause of the diurnal wave is only a suggestion waiting 

 disapproval or confirmation. 



Changes of level are closely connected with rainfall, which, when 

 it saturates a valley has, at one station at least, been accompanied 

 by movements indicating an increased steepness of the bounding 

 hills. Daring fine weather the motion is reversed, or, in other words, 

 the surface movements on the two sides of a valley, with alternations 

 of fine or wet weather, have corresponded to a concertina-like opening 

 or shutting of the same. Certain seasonal changes in level may in 

 part be due to the removal and replacement of loads represented by 

 leaves and plants. 



The last group of movements on which I shall touch are pulsations 

 and tremors, the existence of which are supposed to be indicated by 

 the regular or irregular swingings which are from time to time 

 established in pendulums and other forms of apparatus which are 

 delicately suspended. The occurrence of the latter movements, 

 which have been so carefully studied for many years in Italy, and 

 automatically recorded in Japan, show remarkable relationships to 

 the localities where they are observed, the instruments by which they 

 are recorded, to the seasons, the hours of the day and night, and to 

 a number of meteorological phenomena. 



In Japan, tremors were never observed underground upon rock 

 foundations, which, however, has not been the case in Italy. At one 

 station they may be marked, whilst at another station, only a few 

 hundred yards distant, they may be only shown feebly or be entirely 

 absent. A light horizontal pendulum is usually more disturbed than 

 one that is relatively heavy. Tremor frequency and tremor intensity 

 are more frequent during the night than daring the day. A favourite 

 hour for tremors to appear, or to attain a maximum, is about 6 a.m., 

 and at one station they were always to be seen between midnight and 

 this hour. They are much more frequent during winter than during 

 summer, when barometric changes are rapid, and when the observing 



