DYNAMITE. 



EARTHQUAKES. 



223 



Dr. Duffield has left but few memorials of his 

 rare abilities and his profound scholarship be- 

 hind him. Two or three volumes, not of great 

 size, a score or more of occasional sermons and 

 addresses, many able contributions to theologi- 

 cal and literary reviews, and a volume, as yet 

 unpublished, of reminiscences of his own life 

 and times, are all his contributions to posthu- 

 mous fame. 



DYNAMITE. The dynamite of M. Nobel 

 is nothing but nitro-glycerine absorbed in 

 highly porous silica. It consists of 75 per cent, 

 of nitro-glycerine and 25 per cent, of porous 

 silica. Hence it appears to possess only three- 

 fourths of the power of nitro-glycerine, the 

 specific gravity of both substances being very 

 nearly the same. But, practically, there is no 

 advantage in the greater concentration of power 

 of nitro-glycerine. It ought not to be poured 

 direct into the borehole, since it easily causes 

 accidents by leaking into crevices, where it 

 explodes under the miners' tools. It must, 

 therefore, be used in cartridges, which leave 

 considerable windage ; whereas dynamite, being 

 somewhat pasty, easily yields to the slightest 

 pressure, so as completely to fill up the sides 

 of the borehole, and leave no windage what- 

 ever. For this reason a given height of dyna- 

 mite charge in a hole will contain quite as 

 much nitro-glycerine as when the latter is used 

 in its pure liquid state. As a test of the power, 

 a cylinder, of 11 -inch diameter and 12-inch 

 height, of best scrap-iron, and cut off a shaft, 

 was bored through the centre with a 1-inch 

 borer, and a charge of six ounces was put in with- 

 out securing either end by any sort of plug or 



tamping. The cylinder was blown with such 

 violence against a three-quarter inch boiler 

 plate at some distance as to break it. As a 

 test of safety, a box containing about 8 Ib. of 

 dynamite (equal in power to 80 Ib. of gun- 

 powder) was placed over a fire, where it 

 slowly burned away ; and another box, with 

 the same quantity, was hurled from a height 

 of more than 60 feet on the rock below, no 

 explosion ensuing from the concussion sus- 

 tained. At Stockholm, a weight of 200 Ib. 

 was dropped from a height of 20 feet on a box 

 containing dynamite, which it smashed, of 

 course, yet no explosion took place. Such a 

 test can leave no doubt that dynamite offers 

 sufficient safety against concussion for all prac- 

 tical purposes ; and a Prussian military com- 

 mission recently reported that it appears to be 

 the safest of all known explosives. The great- 

 est drawback on nitro-glycerine is its liquid 

 form. 



Nearly all the calamities caused by nitro- 

 glycerine have been owing to leakage, which, 

 for practical reasons, it is very difficult to pre- 

 vent, and are, therefore, indirectly chargeable 

 to its liquid state. A substance sensitive to 

 concussion, unless it is quite unmanageable, like 

 chloride of nitrogen, can easily be protected 

 against accidents by wrapping it in a soft ma- 

 terial ; but if that substance is a liquid and a 

 leakage takes place, it becomes subject to the 

 danger of direct percussion ; and if nitro-gly- 

 cerine in that condition becomes exposed to 

 the sun's rays, the heat which it takes up ren- 

 ders it so sensitive as to become dangerous 

 under the slightest blow. 



E 



EARTHQUAKES. The year 1868 was re- 

 markable for the number, the wide-spread dis- 

 tribution, and the highly destructive effects of 

 the earthquakes which occurred. They were 

 characterized by a great variety of sublime and 

 wonderful phenomena, rivalling in all respects 

 the most violent earthquakes of which history 

 has made record. 



In the Island of 'Hawaii. The first of these 

 terrestrial convulsions worthy of special men- 

 tion commenced on the 27th of March, in the 

 island of Hawaii, one of the Sandwich Islands. 

 On that day the great volcano, Mauna Loa, be- 

 gan to eject immense columes of lava, and 

 simultaneously shocks of earthquake set in. 

 During twelve days succeeding there were (esti- 

 mated) two thousand shocks, followed at inter- 

 vals by fearful tidal waves, destroying villages 

 and large numbers of their inhabitants. The 

 first outpouring of lava came down the moun- 

 tain-side in a broad stream several feet deep, 

 and travelled with such rapidity, that a family 

 living in its path, two miles from the point 

 where it broke out, had barely time to escape, 

 taking with them only their clothes. The lava 



pushed onward toward the sea, which it en- 

 tered, driving the water back with great vio- 

 lence, and forming a point or artificial tongue 

 of land, at least one mile in length. The smoke 

 thrown out of Mauna Loa at this time rose to 

 a height (estimated) of seven and four-fifths 

 miles, obscuring every thing for a great dis- 

 tance around, excepting when bright spirals 

 of flame shot up from the mouth of the volcano. 

 The severest shock occurred on the 2d of April. 

 At the village of Waischinathe earth burst open, 

 and a tidal wave rushed in with great velocity, 

 sweeping over the tops of the high cocoanut- 

 trees and carrying death and destruction in its 

 train. Vast bodies of earth were torn from the 

 mountain-side and thrown to considerable dis- 

 tances. It was reported that the slope and part 

 of the summit of a mountain, fifteen hundred 

 feet high, were lifted up by the earthquake and 

 hurled over the tops of the trees to a distance 

 of over one thousand feet. On one side of 

 Mauna Loa a singular eruption of moist clay 

 occurred, covering a space about two miles 

 and three-quarters long and one mile broad. 

 This was followed by an immense stream of 



