18 AWIAI. REPORT OF THE 



60 feet, and since the "Cambridge shales" are met with in front of 

 Memorial Hall at about 12 feet below the surface. The two arms 

 or components of the tromometer stand X. 3° E. and N. 93° E. re- 

 spectively, according to a determination of the meridian passing 

 through the station. The latitude and longitude of the station 

 determined by comparison with the position of the Astronomical 

 Laboratory, arc as follows: — Lat. 42° 22° 36" X., Long. 71° 06' 59* 

 W. from Greenwich. The altitude of the pendulums as compared 

 with the local contour of the city engineer's map is provisionally 

 determined as 7 meters above mean sea-level. A brief account 

 of the station has been published in The Harvard Bulletin for 

 April 29, 1908. 



At present the pendulums are working without a damping 

 device. The latter has, however, been ordered from the manu- 

 facturers. The first distinct earthquake record was obtained on 

 the morning of May 15, 1908, at 3h. 39m. 43s. as indicated by 

 the north-south component. The east- west component did not 

 record the trembling until 3h. 47m. 5s. The time of maximum 

 motion was 3h. 45m. 35s.; and the end of the record came at 4h. 

 19m. 15s. The arrangements for obtaining exact time are as yet 

 unsatisfactory. The recording of the beginning of the preliminary 

 tremors at this station in the above-mentioned earthquake at a 

 time somewhat earlier than was noted in Washington may be due 

 to the greater sensitiveness of our instrument. Some trouble has 

 been experienced in the rusting of important wires which support 

 the pendulum. It is hoped soon to obviate this difficulty. The 

 chief expense in the maintenance of the tromometer is likely to be 

 the cost of the fixative solution for the smoked paper, and of the 

 paper used for the records. In ordinary practice a skilful manip- 

 ulator can change the records, fix the smoked paper, and adjust 

 the pendulums in half an hour. This work is done between 8 and 

 and 9 A. M. Mr. G. M. Flint is doing the work with care and 

 promptness. To avoid the possible wrecking of the booms of the 

 steady masses, should the suspending wires break, a block has 

 been placed under each weight with less than a quarter of an inch 

 windage, w T hich allows a free swing of the pendulum and serves 

 also as a support on which to lower the pendulum when it is neces- 

 sary to dismantle it. 



Arrangements have been made with Professor H. F. lleid, of 



