Kettlewick Observatory·Seismograph No. 2·Vertical Component

Founded on the rock, 1894. Observatory time runs at six times the pace of yours.
FIG. 1 — ELEVATION 20 cm escapement, beats ½ s stylus & time-marker boom, aluminium, 1·2 m rider vane in castor oil mass, 80 kg
Rack of previous days
Sheet No. 2318, put on — G.M.T. 1 line = 1 min · V × 5 · T₀ 1·5 s Knock anywhere on this page, or press SPACE — the pen will hear you.

Ledger of Disturbances kept by the observer in charge

G.M.T.S − PMax. amp. mmRemark

How to Read the Record

The first sharp tremor is P, the push-and-pull wave that travels fastest; the second, larger and slower, is S, the shear wave. Count the seconds between them: each second of S − P puts the shock roughly nine kilometres farther off. The long rolling swell that follows, L, has come the slow way round the surface of the Earth, and its height tells the size of the shock.

Visitors are asked not to stamp. — E. Marrable, Observer