WelUnijton PJiilosojjhical Society. 521 



similar wave was observed in New Zealand, after which we had news of an earthquake in 

 America, and no doubt the wave on the 11th of last May was due to a lilce cause. 



Dr. Hector said the tidal disturbance on the 11th of May had been observed on every 

 part of the New Zealand coast, and also in Australia in the same manner ; but not so 

 intensely as the waves of August, 1868. The origin of the waves on that occasion was 

 clearly traced to a great volcanic disturbance near the west coast of South America, and 

 in this instance a violent convulsion has also been reported from that quarter as having 

 occurred on the 10th of May. We have not the full particulars yet, but if this date is 

 correct the wave felt on our coast must have been due to a still earlier shock, perhaps 

 in some other place, as it was first noticed at 5 a.m. on the 11th, corresponding to 1 p.m. 

 of the 10th on the South American coast. From this date must be subtracted about 

 seventeen hours for the time of the transmission of the wave across the Pacific Ocean, 

 which would require that the shock should have taken place about 8 p.m. on the 9th. 

 This tends to confirm the belief that there is a periodicity in earthquakes, and that they 

 occur independently at distant localities at nearly the same time. He observed that a 

 writer in the last received number of Nature notices this coincidence in reporting a sharp 

 earthquake at Comrie, in Scotland, on the 11th of May. At Napier, where the engineer 

 of the harbour works, Mr. Weber, makes exact observations, the tides were disturbed 

 from the 11th to the 19th. The position of Napier renders it peculiarly sensitive to 

 oceanic oscillations. Thus, on the 1st of May the highest tide ever experienced in Napier 

 washed over the shingle spit, and damaged -the rails in front of the Court-house. This 

 phenomenon was, however, local, and was attributed only to a long continuance of south- 

 east wind. He called attention to a recent paper by Mr. Eussell, the Government 

 Astronomer at Sydney, which states that the slightest earth-shocks felt in New Zealand 

 are nearly always recorded on the tide-gauges in Sydney and Newcastle, and are most 

 unaccountably coincident with abnormal readings of one of the thermometers in the 

 Observatory.* If we had well-placed tide-gauges on the New Zealand coasts it is probal le 

 the most interesting results would be obtained. Every addition to the observed facts 

 bearing on this subject would be valuable. The investigation of earthquakes would be 

 similar to that of the influence of sun spots recently examined by Professor Balfour 

 Stewart, in so far that the release of prodigious latent energies might depend on very 

 obscure and trivial exciting causes. 



Mr. Carruthers said he did not consider it necessary to suppose that seventeen hours 

 must elapse before a tidal wave, due to the same cause as the South American earth- 

 quake, would reach New Zealand. He did not think the earthquake caused the wave, 

 but that both were due to the same cause. He thought earthquakes were locally 

 intensified exhibitions of a great deep-seated movement of the floor of the ocean, and 

 that, if the floor were not in movement, an earthquake, however violent, would be unable 

 to propagate a wave for such a distance as from America to New Zealand. The intensified 

 action which so often shows itself in a part of South America he thought was due largely 

 to the great bend made in the line of elevation of the Andes at this point, which had the 

 effect of converting a deep-seated movement of the earth's crust into a violent crushing 

 of the surface. 



Dr. Hector explained that the period of seventeen hours for the transmission of a 

 wave across the Pacific Ocean was derived from observation in 1868, when the com- 

 motion of the sea extended not only to New Zealand and Australia, but to Japan, the 

 Sandwich Islands, and the Cape of Good Hope. He agreed that earthquakes were wide- 



* Trans, E. Soc, N.S.W., 1876, p. .37. 



pa 



