GEOLOGY AND MINERALOGY. 257 



VELOCITY OF EARTHQUAKE SHOCKS. 



Mr. J. Brown, in a communication to the British Association, pro- 

 poses to estimate the velocity of Earthquake Shocks in the laterite of 

 India, a clayey rock in a semi-pasty condition of perhaps the lowest de- 

 gree of elasticity, reposing in some places on strata of sand and clay. 

 Supposing the shock to have-'lravelled from Quelon to Trevandrum, 

 and taking the distance between these two places at thirty-seven 

 miles, a velocity of propagation is obtained at between 470 and 530 

 feet per second, according to the time marked by different observers. 



DESTRUCTIVE EARTHQUAKE IN THE STATE OF SALVADOR. 



A letter from San Salvador of the 28th December, 1859, reports 

 the occurrence of a fearful Earthquake on the night of the Sth of that 

 month. It commenced about a quarter before nine, and continued 

 for two minutes and 35 seconds. At Isalco the parish church was 

 destroyed, except a portion of the naves and the sacristy. About 40 

 of the best houses and a number of smaller ones were destroyed ; 

 fortunately no lives were lost. During the night several other 

 shocks of more or less severity and duration were felt. One of 

 them, more violent than the others, completed the destruction of 

 some buildings that had escaped the first shock . The shock was felt 

 at Guatepeque, Opico, Apopa, Tepecoya, and other towns. At 

 Tepecoya the church, cabildo, and several houses were destroj-ed. 

 At Guatepeque the church and cabildo partially. Iaguaque suffered 

 also, several houses were destroyed, and the church greatly in- 

 jured. On the outskirts of the town great holes were opened, some 

 over 100 yards wide. At Guayamoco houses were destroyed, and 

 the church much damaged. At Panchimalco, houses injured, and 

 large holes opened in the earth. San Martin and Comasagua, church 

 and cabildo partly destroyed. Nanhuisalco suffered also, and soon 

 after a destructive fire broke out which burnt over 200 houses, — thus, 

 in a measure, destroying the whole place. On the night of the 10th, at 

 9.30, there were two more severe shocks. On both occasions the 

 nights were very clear, but blowing a heavy norther until a short 

 time before the shocks, when it fell calm, but again rose soon after 

 the shocks. The Volcano of Izalco was, no doubt, the centre of 

 vibration, as the shocks were felt all around, but most strongly in 

 the N.E. direction, and for a distance of 150 miles, as far as known. 



EARTHQUAKE IN CORNWALL. 

 An Earthquake Shock through nearly all Cornwall, on the 13th 

 January, 18G0, at 10.32 p.m. (local time), during a squally and un- 

 usually dark night, appears to have been the severest recorded in 

 this county. It was felt at great depths under ground, in several 

 mines very distant from each other, although not in any of the mines 

 "f St. Just, on the west of Penzance. On the surface, however, in 

 almost every locality, the persons who felt it were probably twenty 

 times more numerous than those who experienced the shock of the 

 21st of October in the previous year. 



