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J ^ '• ■ '. : for the Advancement of Science. ▼*%'-*. 421 



; Ae stream of liquid red-hot' iron as it pass^ll from the furnace/and af. 



■ terwards scooping out portions of iron from the casting ladle, uniil the 



# fluid sunk fo the merp red-hot fluid state, when danger might be-appre- 



,v bended from the falling of jiie temperature causing the iron to adhere. 



^ .. 4. Oa ^ar/Aguatcs ; by Mr. Mallet. 



Mr. Mallet presented^is '^Second Report on the Facts of Earth- 

 quakes,*' and stated the result of his experiments for the " Determina- 

 tion of the Limits of Earthquake VVave Transit," for which the pro- 

 posed pl^n was explained last year. The rate of transit was expected io 

 . be the least rapid in sand, and most in some elastic, homogeneous, crys- 

 talline rock. Accordingly, a mile was measured on the sands near 

 Dublin, and a cask of powder buried at one extremity, — the interval 

 between the firing of the powder and the indication of the shock at the 

 other station, as registered by Wheatstone^s chronograph, gave a rate 

 of 965 feet per second, as the average. of ten good experiments, A 

 shorter base was measured on the granite, and shocks produced by 

 borings three and a half inches diameter and eighteen feel deep, in 

 which as much as twenty pounds of powder were exploded. The ex- 

 periment was repeated twenty or thirty times, — and where the granite 

 Was most shattered the shock arrived at the rale of only 1,299 feet per 

 second; under the most favorable circumsiances, where the rock was 

 most homogeneous, the impulse travelled at 1,661 feet per second. In 

 tT^any of the most celebrated earthquakes, clocks have been stopped, 

 and thus indications affurded of the rate at which the shocks travelled. 

 In the Lisbon earthquake of 1761, the shock travelled to Curunna at 

 the rale oT h994 {(:iel, \o Cork at the nxie of 5,280 feet, and to Santa 

 Cruz in Barbary at 3,261 feet per second. The great Cutch earth- 

 quake, in 1819, stopped the clocks in Calcutta, and showed a rate of 

 1,173 feet per second. The Nepaul earthquake of 1834 stopped nu- 

 merous chronometers, and the rate of transit from the assumed centre 

 to various places showed a rate varying from 1,000 \o 3,000 feet per 

 second. These rates were all lower than would be expected, consider- 

 ing rocks as homogeneous substances ; and perhaps, after all, the earih- 

 . • quake shocks might follow a law altogether different from thai of 50uwi 

 Waves. 



Mr. Maliet then called attention to the Catalogue of Earthquakes, 

 amounting to nearly 6,000, and — exhibited diagrams in which the 

 amount of earthquake disturbance in all known times was represented 

 by curved lines; these showed a slight indication of paroxysmal peri- 

 ods, with intervals of half a century or more- Another diagram rep- 

 resenting the months in which the shocks occurred, showed a maximum 

 in December and January. Mr. iMallet then exhibited a map of the 

 distribution of earthquakes, formed by coloring the area of each suc- 

 cessive earthquake recorded in the Catalogue, and one wash of color 

 being carried over another, produced tints of intensity proportioned to 

 the frequency of these visitations. On this map the regions of Guinea, 

 Abj/ssinia, and Madagascar were uncolored, no recorded earthquakes 

 having occurred in them; Greenland was uncolored, because the slight 

 shocks felt there miaht have been occasioned simply by movements of 

 Kiasses of ice upot^he coast. Special attention was called to one spot 



Second SEaiEs/Vi^l^XII, No. 36.— Nov., 1851. 5i 



