NEW SEISMOGRAPH.

Hokitika Guardian, 7 February 1923, Page 4

NEW SEISMOGRAPH.

A DELICATE INSTRUMENT. j J NSTALLAITON AT KERB URN. J WELLINGTON, Fob. A. j "What ve arc all aiming at is Ijt? ill "S, lile to prcclift earthquakes." stated I),- Adams .Government Astronomer) at Kelbiiril Ohscrcatory, alongside which , preparation* are now being made tor j the installation of a new s (; isinograph, i „r • ’earthquake detector.'’ as it might- I he called. ‘'Before we can hope to do ( that, however, we have to follow the j ordinal scientific coarse, by proceed-, inn to collect precise date ot what is j happening in the earth. A\ e. therefore. need, a delicate instrument which i will at-once record and measure all the | thrusts, strains, tremors, and quakes ( that take place; and hy studying thou-: sands upon thousands ot these refolds. ; measuring and comparing them with infinite care, we may hope to he tilde . at length to say that such and such a 1 record means that an earthquake is. due within a longer or shorter period of time. That is why we are new pro-, paring to install alongside tin* ohsi , - vatory a Milnc-Sh-aw seismograph--as improved hv .Mr .J. -I- Shaw. (Ills i* the machine reeommeinled hy the chief British seismidogical authority, i We had the machine installed temper- ; arily at the Victoria College tor exhihi'tiuii at the Science Congress; hut a permanent home is to he built for it here at the observatory. I hat big pit you saw being dug beside the , door of the observatory is for a roll- , Crete block or pillar. I'-’ft high on which the seismograph "ill rest, so as t,, he free from mere sUilaee vibrations." FORTY TIMES MORE SENSITIVE. Showing our representative a mini- ] her of the daily record- made by the | machine at \ ii-toria l ollege, Di Admits -tilted that it is forty times : sensitive a- the old Millie machine, j which was previously the only seis- I timgraph we had in New Zealand, j "The result is," be said, "that work- ; ing with the new machine is like working with a microscope forty times more powerful than you have been used to working with. Aon will note j ''comparing the records) llicl the iecords of the old machine show only a , straight line till a distinct quake is ; registered ; hut. the new machine show* a serrated line, like the teeth ol a j small saw, demonstrating L11: 1 1 '-he crust of the earth is in constant motion. That is to say, there are in- ' cossant. minute oscillntions oi t!i<‘ ground. You will note, too. at large!' or shorter intervals a movement oi the whole line to one side or the other hv about its own width. That seems to indicate a sideways thrust, easing 1 od when the line comes into 'position , '.I'VERY SENSITIVE INSTRUMENT : •■And what is that big jump of about - a quarter of an inch, first to one side and then to the other,” a-ked our ren resent a live. ■ "That,” replied Dr Adams, "registers where 1 stood first at one side ol the machine and then at the ot her. ; That shows how extremely sensitive the machine is. though its foundation is supposed to he quite isolated from the floor of the room. On •L'liuary -•-lid Anniversarv Day. you will note a distinct earthquake was recorded from the oscillations shown 1 should judge that it was some considerable distance a wav possible in the direction of Tonga, 'where we get a lot of earthquakes. The one machine, however, can only indicate the radius within which toe earthquake occurred not its directum, north, east, south or west as the case innv be. The direction will not he onta'iimblc until a second machine, mounted at rigid angles to the first. •> . available. PHOTOURARDR RECORDS,. 1. the case .of the new machine the tremors are recorded photographically by a beam of light, reflected on a particularlv sensitive mirror ami Rich tin-own back on to a recording drum, covered with bromide paper and o’voicing in a light-tight box or camera. There is thus no friction in the rocoi-i----of the movements, such as is inevitable when the record is made >y means of a pen on a revolving drum. When we have accumulated a large number of these records wo >h.d 11 able to studv and compare them, so as to understand what they mean tn the way uf changing thrusts and strains and various movements of the earth’s crust; and we hope that grit- j dnallv this studv of the records will load ' tip to our being able to predict ; both when and where earthquakes are! coining. Tin- record slips of bromide j paper are changed once a day. each slip wound round the drum giving us a record for the whole twenty-four hours. ; Then the records have to he developed j like any other photograph. It is, verv interesting, in fact, in its way. ex- j ciiiug work. A oti know what it is to j go fishing .with what excitement you - watch your line to* rod tor an indication of a nibble or a bite. Well. I watch the development of the records for- a tremor or a ’quake, with just as much excitement as a fisherman watches his line or his rod. It is. in a way, li-lv ing for earthquakes.”