Review of Reviews, 1/6 f06. 



THE MELBOURNE EARTHQUAKE RECORDER. 



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Fac simile of the ribbon on the Seismograph at the Melbourne Observatory, showing the effect of the San Francisco 



Earthqual<e Shock as felt in Melbourne. 



[Mr. Barncchi, tlie Victorian Government Astronomer, very graciously accorded to a representative of " The Ee- 

 view f E views" an interview upon tie interesting record made in the local observatory, when the San FranciBco 

 earthquake took phice. The result is c-iven 1 erewith, and also a reproduction o£ the ribbon of the seismograph at 

 that part where the shock is recorded. — EdiTOE.] 



The seismograph room at the Melbourne Ob- 

 servatory' is in one of the .small basement rooms, 

 with all natural light excluded. The first ap- 

 pearance of the prone seismograph, with a 

 small lamp kept constantly burning at the near 

 end of its six or seven feet of length, recalled 

 vividly to the ^Titer's mind the gruesome im- 

 pression he once received, on viewing at night, 

 in an English hamlet where the custom still holds, 

 the dead body of a resident. There is no sentiment 

 in the seismograph, however; the lamp itself 

 serves a scientific purpose, the Government Astro- 

 nomer's only thought was to explain the mechanism 

 of the machine, and his only care to see that the 

 carele-ss layman he had rashly introduced into so 

 holy a place did no damage. The layman is even 

 now full of thankfulness that in his ignorance he 

 did not produce an earthquake record, representing 

 a shock which might have left the city of Melbourne 

 in as ruinous a condition as that in which San Fran- 

 cisco lies at the present day. The way of it was 

 this. The ^vriter, in the midst of a lucid explana- 

 tion by Mr. Baracchi, approached the record box 

 with the intention of using it for a support in making 

 notes, when an agonised exclamation, " Oh ! don't 

 touch that !" warned him just in time. Had he 

 touched the record box, there might hav& been a 

 vibration, consequently a record. The seismograph 

 does not lie ; ergo, an earthquake on that particular 

 date. 



Briefly, the seismograph is an instrument, the 

 foundation of which is a pillar of masonry reaching 

 down into the earth to bed-rock. On this pillar, 

 boxed in of course, there is a delicately poised mast, 

 to which is swung an aluminium rod, technically 

 kno\vTi as a boom, about three feet long, which is 

 connected with the recording box. On the recording 

 box a small lamp is kept constantly burning, the 

 light of which is reflected downwards from a small 

 mirror through an aperture at the end of the boom 

 on to a ribbon of bromide photographic paper. 



The ribbon moves constantly at a speed regulated 

 by a clock in the recording box, and in normal 

 conditions a thin regular line is drawn down the 

 centre of the ribbon. When an earth tremor comes 

 along, the boom sways horizontally according to its 

 intensity, a wider portion of the ribbon is exposed, 

 and an accurate photographic record, so to speak, 

 of the tremor is thus produced. The ribbon is two 

 inches wide and thirty-five feet long, and unwinds 

 automatically at the rate of five feet a day. Once 

 every hour a pointer in the clock falls and a notch 

 is produced in the edge of the ribbon. Conse- 

 quently, the exact time, to the second, at which a 

 tremor occurs is duly recorded. Once a week an 

 attendant) visits the room, takes off the completed 

 roll, fixes another, and winds up the clock. Daily 

 he calls to trim the lamp and listen to the ticking 

 of the clock, after which he departs, presumably as 

 quickly as possible. The notches on the reduced 

 fac-simile of the strip of ribbon shown on this page 

 indicate the hours from 11.30 p m., April i8th, to 

 2.30 a.m., April 19th. The partition into seconds 

 of Melbourne statute time is to allow for the un- 

 avoidable but known inaccuracy of the clock. 



The section of the ribbon reproduced shows that 

 the first tremors occurred at 11.43 P-"'- ^n April 

 18th, corresponding to 5.43 a.m. April i8th at San 

 Francisco. The maximum wave was recorded here 

 at 12.42 a.m. on April 19th, corresponding to 6.42 

 a.m., April i8th, at San Francisco. Another shock 

 was recorded here at 5.50 p.m. on April 19th. 



The records show that, allowing for the difference 

 between Melbourne and San Francisco time— 18 

 hours — the earth tremors travelled the intervening 

 distance, about 9000 miles, in a little over an hour, or 

 at the rate of rather more than two miles per second. 

 The seismograph, although it does not appear as 

 frequentlv before the public as the barometer, the 

 thermometer, and other scientific instruments, has 

 generally, when it does appear, a sensational story 

 to tell, and it is sure of a good house. E.iH.W. 



