ON THE FACTS OF EARTHQUAKE PH^ENOMENA. 297 



this advanced season) was too feeble to fire at this distance, and accordingly 

 12 more pairs of plates were added, and the whole of the apparatus removed 

 from the church to a point a little to the westward and within about 250 feet 

 of the most remote hole (A in map, Plate XIV.), where it was found that 

 signals could be seen and repeated from the remoter end of the range by 

 taking advantage of some elevated points of rock. The whole of the scaf- 

 folding, which had cost so much labour and trouble, thus became useless, 

 and a new splinter proof had to be constructed from its materials. 



On the 3rd of October, these new arrangements having been completed, a 

 second preliminary experiment was made, when it was found that the priming 

 cartridges could be instantly and certainly fired with the increased power of 

 Bergin's battery, and that the Smee's battery also released the chronograph 

 at the remote end wall ; in a word, that all was perfect. 



The positions of the instruments were now precisely as already described 

 at Killiney Bay, except that all the firing batteries and apparatus were placed 

 upon a convenient table or platform about 2^ feet from the ground, formed 

 out of the abandoned scaffolding of the church. 



Both the conducting wires were supported on dry wood stakes, from which 

 they hung by loops of gutta percha through the entire distance. The position 

 for the chronograph at the observer's or seismoscope end having been fixed 

 upon, a flat table was cut down upon the face of the solid rock at nearly the 

 most elevated spot upon the island to form an efficient bed for the Seismo- 

 scope, the bottom plate of which was so let into the rock as to be firmly 

 grasped by it, as seen in PI. XV., lower figure. 



Four holes, 1^ in. diam. and 6 in. deep, were jumped in the rock round the 

 Seismoscope, and a canvas screen, stretched on upright inch-round iron 

 rods socketed into the holes, was erected to keep off all wind from the Seismo- 

 scope ; which was found of great service. 



The priming cartridges for firing the blasts had been prepared in a pecu- 

 liar manner, inserted in sticks of dry pine of 8 feet in length, in a groove 

 down one side of which the e+ wire passed, and up a similar groove at the 

 other the e— wire passed, both imbedded in a cement composed of pitch 

 and wax. The priming powder was fine rifle-glazed gunpowder, the 

 copper wires yij^^th of an inch diameter (16 wire-gauge). The platina wire 

 was such that 2 inches weighed 1 '62 grain ; it was wrapped round with gun- 

 cotton, the powder poured round it ; one side of the recess or mortice, which 

 was cut quite through the wood, being closed by brown paper pasted on, and 

 the whole then closed by brown paper pasted over, and also over the whole 

 stick, which was then roughly varnished over witli pitch and wax, laid ou 

 hot so as to exclude moisture (see PI. XVI.). One side of each stick was 

 rounded to fit the curved side of the cylindrical jumper-hole, so as to admit 

 of the tamping being driven well home ; and the enlarged lower extremity was 

 cut wedge-shaped, so as to bind in the tamping when the blast should be 

 fired. 



The priming was so placed in each hole as to be a little below the centre 

 of the depth of the powder, which occupied about 6 feet in depth of each 

 hole, leaving about 6 feet for tamping. The tamping was dry yellow loamy 

 clay, the same as used at the Killiney quarries in the operations for getting 

 granite stone for Kingstown Harbour. The tamping was driven home after the 

 first few inches of clay over the powder with a round iron bar of about |ths of 

 an inch diameter, which was found to work most effectively, and the priming 

 sticks were not found to offer any obstruction to the perfect tamping of each 

 hole. The priming sticks themselves gave a most complete resistance to the 

 explosions for their own section of each hole, as their subsequent condition 

 proved, each stick, with but one exception, being pounded on end into ch?iff. 



