Vol. \II. No. 157. 



THE AGRIUULTUKAL NEWS. 



139 



THE JAMAICA EARTHQUAKE. 



A further e.xtracb from l)r. Vaughan Cornish's 

 paper, dealing with the character and results of the 

 Jamaica earthquake, is given below, in continuation of 

 the notes which appeared in the last issue of the Ar/ri- 

 cultiiral Neivs, describing tiie personal experience of 

 the author in Kingston at the time of the disaster : — 



The ecduomic importance of the Jamaica earthquake of 

 Januaiy 1-i, 1907, is due to the destruction of Kingston and 

 its suburbs, and it is in and around the city that the effects df 

 seismic shock upon buildings can best be studied. Mewed, 

 however, from tlie physical standjioint, the importance of an 

 earthquake is independent of the neighbourhood of cities. 



I think I shall be able to show that the Jamaica earth- 

 quake was e.ssentially doublediarrelled, so to siieak ; that 

 Kingston was brought down by one barrel, and that the other 

 barrel was discharged in a thinly iioiiulated district, where it 

 consequently did much less damage ; but that when we 

 cxauune the seismic effects in parts of the island distant from 

 either of these foci, we find that they are, on the whole, about 

 as nuich due to the one part of the double shock as to the 

 other, the charge in the two barrels, so lo speak, Iieing about 

 equal. From the physical standpoint, tlicri'fore, the Kingston 

 eartlnjuake is not (pute the same thing as the Jamaica earth- 

 (piake. 



Thirty seconds is the duration currently assigned to the 

 earthcjuake at Kingston, but no one really timed it there. 

 At Kellits, about 35 miles north-west of Kingston, Jlr. Horn 

 informs me that the earthqtiake, timed with a watch, lasted 

 37 second.s, this space of time being divided as follows, viz : 

 17 seconds shaking, 13 seconds rolling, and again 7 seconds 

 shaking, which finished with a distinct jerk. At Bethan}-, 

 alxiut 45 miles north-west of Kingston, Dr. Hargreaves 

 informs me that he timed the earthquake by a seconds hand 

 watch, and found that it lasted 30 seconds. 



I have described the character of the vibrations which 

 I experienced in a top story corner room of a brick house in 

 East (Street. These were only in a secondary sense due to 

 the earthquake, the immediate cause being the actifm of the 

 vibration of the massive walls upon the wooden floor. The 

 movement of the ground was well observed opposite the old 

 Mico, in Hanover Street, by Sub-Insjiector Trenilett, and 

 near the .south end of John's Lane by Mr. ."^ullivan. In 

 addition to any jarring or Vmmiiing, there was a strong swell — 

 liteially a groiuid swell — running from west to east or east to 

 west. .Mr. Sullivan says the west-to-east roll was much 

 stronger that the return roll from east to west. The inqires- 

 sion generally received was that these surface undulations 

 were only a few yards from crest to crest, and they certainly 

 succeeded one another several times in a second. The height 

 from crest to crest appeared to be several inches, so that 

 their steepness was very considerable. A.s far as I am aware, 

 the only instrumental evidence as tci the jjeriodic time of the 

 earth((uake oscillations is that afforded by the transmitter of 

 the West India Direct Cable to Kingston. I learnt that it 

 had continued to run for a time before the office collapsed, 

 and that the strip of paper had been sent to the London 

 office as a curiosity. I therefore timed 4he running of the 

 machine in Kingston, and afterwards in Ijondtm was allowed 

 to measure the osi'illations of the writing jjen as recorded on 

 the strii> of [laper. There were ten complete nortli-south- 

 north o.scillations in the first two and a ha)f seconds, i.e., four 

 per second. The position of the instrument did not |)ernut 

 it to record east-and-west vibrations. 



I carefully examined a large number of buildings in 

 Kingston, which is a brick town, to ascertain the line, 



or direction, and the sense in which walls had fallen. The 

 town is laid out rectangularly, houses facing the four cardinal 

 )K)ints, and in the detached hottses east- and west-facing, outer 

 walls generally fell, while this fall of north- and south-facing 

 walls was an exception except in the area of greatest damage. 

 Oi the east- and west-facing walls many more fell to the east 

 than to the west. In the neighbourhood of North Street, 

 east of East Street, which I exannned in detail, I found that 

 of the north- and south-facing walls more fell to the south 

 than to the north. Thus the walls tended to fall, in most 

 cases, towards a little south of east, liut in some cases, a little 

 north of west. 



I consider that the fall of these walls was due to the 

 action of the surface waves above described in tilting the 

 walls out of the perpendicular, first in one direction and then 

 in the other, causing them to sway. If the waves were short, 

 as they appeared to be, and as I think they were, the lower 

 pai-t of the wall was thrown very much out of plumb at each 

 half-swing, and a wave of displacement travelled up each 

 wall, so that it became sinuous in f(]rm and was subjected to 

 rippling uKivement. 



The mere rapid jsrring vibration, which w^is so marked 

 a feature of the sen.sations of the earthquake, probably had 

 little effect in overthrowing walls. The north- and south- 

 facing walls, which did not usually fall, were equally exposed 

 to this form of vibration, which seemed to come somewhat 

 steeply from below-. These walls were rocked longitudinally 

 by the east-to-west or west-to-east waves (instead of swaying 

 transversely), and the effect was to produce a double system 

 of cracks, often going through the whole thickness of the wall 

 liut not throwing it out of plumb. As the wall returned 

 westward from its eastward excursion, a crack formed, owing 

 to the want of tensile strength in lirickwork or masonry, the 

 eastern end of the wall being, so to s[ieak, left behind. On the 

 return vibration in an ea.stward direction, a corresponding 

 crack opened at the west end, and these cracks often cross 

 each other diagonally, as some ot my photographs show. 

 Walls in which cement mortar had been used stood much 

 better than those with only lime-mortar. Kingston lime- 

 mortar is generally of poor quality. The defect of all stone 

 and brickwork, however, in resjjcct to earthquake shock, is 

 want f>f tensile strength, hence the advantage of reinforcing 

 concrete, etc., by strips of metal, which give a fibre to mate- 

 7-iats otherwise two brittle. The disadvantage of extra height 

 and tojj weight were, of course, abundantly in evitlence. 

 .^ny departure from simplicity of form usually brought about 

 additional damage, (Jothio gable and classic cornice being 

 almost equally unsuitable in earthquake countries. In face of 

 these restrictions it seems that architects in earthquake coun- 

 tries nuist rely mainly upon the skilful proportioiung ot 

 spaces lor the prodm-tion of artistic effect. 



CANADIAN EXHIBITIONS. 1908. 



The Impeiial Comnihssioner of Agriculture has 

 received the following 1-etter from Messrs. Pickford and 

 Black, in reference to the dates of the Canadian 

 Exhibitions to be held in 190.S :— 



A\'e yesterday received your cable asking for dates of 

 Toronto and Halifax Exhibitions and confirm our reply this 

 morning. The Toronto Exhibition opens on August 29 and 

 chises on September 14 ; the Halifax Exhibition opens on 

 September 2, and ckises on September 10 : therefore it will 

 7iot be possible for the exhibit that goes to Toronto to be 

 exhibited at Halifax. We will then probably only exhibit at 

 Toronto, unless the West Indies send two sets of .samples. 



