The Problem of Earthquakes.

Horowhenua Chronicle, 19 September 1910, Page 4

The Problem of Earthquakes.

lU3MAR K A l?L E INSTR U.M UNT

A wonderful new instrument to record the motion of the earth produced by an earthquake, however distant from the recording station, lias been invented by the distinguished scientist, Prince Galitzin, member of the Imperial Academy of St. Petersburg. By the application of ingenuous contrivances the seismograph gives an actual scale reproduction of the earth movement, unlike other earthquake recorders, which continue to vibrate uiuler the earth's initial movement long after that movement has subsided. The new instrument lias 'been mounted at Kskdaleinuir Observatory, Dumfries-slure. The following is the official description :

Fundamentally the instrument consists of a horizontal pendulum suspended, by wires, so that when the framework which is attached to the earth by a pier is moved, the pendulum is .set in motion. In this respect it resembles other torms of

SEI SMOCrR.A PT'HS. notably that of Dr .Milne, to whom indeed we niainlv owe the principle. In the absence of friction such a pendulum would continue to vibrate lone; after the earth movement has ceased, so that it is impracticable to attempt to determine from the motion oV the pendulum the earth movement which produced it.

If, however, _ friction is introduced, the motion 'if the pendulum rapidly subsides, mid by suitably choosing the amount of frietioi the instrument can be made what is technically called "dead-beat." In , this condition (he motion of the ■pendulum _ is, evept in om or two very special eases, an exact reproduction on a certain scale of the earth movement. In the Galiiizin pendulum such friction is introduced bv allowing a copper plate aMached t'o the non~ dill 11 rn to move between (he pules of a strong magnet. According to the_ laws of ole'tro-magnetism the friction so produced conforms to a MOST PRECISE and simple hi v.-. In fliis wav the Sicofn 7 'V>v-v^'I 1 h ' indicate pieusoly ov Us ihoMoii motion of the earth. The introduction of (his friction ias, however, a <K.sp.fh. V n , c n Irtu,,.. sensiiiVtMiV-". iii-' cmapparatus. But by a second brilliant application of electro-mag-netic theory Prince Oalitizin has overcome this trouble. A coil of viro attached to the pendulum moves between the poles of a strong magnet and an electrical currenl is so genera ted in (he coils when the pendulum is moved. These currents are carried to a galvanometer timed to Hie same fundamental period as tlie pendulum and again made "dead beat." Thus the motion of (he earth is reproduced 011 the galvanometer with perfect precision on a scale of magnification sufficient to satisfy tho humblest observer.

A mirror attached to the galvanometer reflects a

TINY DOT

of light from a. lamp on to a sheet of photographic paper. The papei is attached to a circular drum driven by clockwork, so that if there is 110 earth movement the dot traces a straight line on the paper. If an earth movement ocelli's the dot is moved sideways and a complete and proportionate record of any movement of the earth is reproduced on the photographic paper. As no man can predict the direction from which an oarthr|iiako may proceed two pendulums with corresponding galvanometers nre required to give a record of the offeet coming from north to south and from east to west. The two dots of light record the earth movement on the same photographic sheet, and thus nn almost cursory examination of the record shows the direction from which the earthquake proceeded. Precise measurement, combined with principles already pstablished enabled an observer at a

SINGLE STATION to assign with considerable preeiX,? 0 " f ' nn ™rihqnakc disturbance. Thus Prince Gili.t fin at St. Petersburg umld "st riom his records whether a n "earthrte rrod at " r