Welsh Journals

THE CARDIFF SEISMOGRAPH. By E. WALFORD, M.D. The Seismograph presented to the Cardiff Corporation by the Naturalists' Society on 20th December, 1909, is of the Milne Horizontal Pendulum pattern. It is housed at the Meteoro- logical Station, Penylan, Cardiff, 203 feet above mean sea level, in a detached brick building built specially for the purpose. The Seismograph stands on a cement-concrete column eighteen inches square, three feet above the floor level. The circular base of the column, which is five feet in diameter, runs four feet into the ground, and is detached from the floor of the room. The clock box and other recording parts of the instrument are fixed on a strong wooden table, the legs of which are securely fixed in the concrete floor. The « Seismograph consists of an iron stand and upright, carried by three levelling screws, which rest on a slate slab on top of the concrete column. A metal pivot projects from the lower part of the upright, against which a horizontal aluminium boom rests. The end of the boom resting against the pivot is cup-shaped in order that the boom may be kept in position. The boom is held in a nearly horizontal position by means of a tie (fine wire), the last inch or so of which is of unspun silk, fastened to a screw at the top of the iron upright, and also to the boom a few inches from the projecting pivot. At this point a thread is attached to a small upright and to the boom, about nine inches from the outer end, to prevent the boom from sagging. On the boom, between the pivot and the wire attach- ment, rests a weighted cross-bar for the purpose of obtaining the "steady point." This cross-bar also serves the purpose of balancing the weight of the extreme end of the boom.