ON THE FACTS OF EARTHQUAKE PHENOMENA. 



291 



precluded communication by the voice. Three bannerols, blue, red and 

 white, being provided for each end, a signal man (Sergeant Maberly, R.A. 

 at the firing end, and a Gunner at the observing end), each with a look-out 

 man provided with a telescope, was stationed at either extreme. All signals 

 made were repeated in the same form to show that they had been observed 

 and understood. 



Signal Code. 



White flag Charge the mine. 



White and red Make connections. 



Red Prepare to fire. 



Red dropped Fire. 



White and blue Priming or charge has fired. 



Blue and red Stop. 



Blue and red dropped Proceed. 



Blue Send and receive message. 



A man was stationed at half-distance to go to either end on being signalled. 

 These signals were found sufficient, and after a little practice to work well ; 

 but on the latter days of experiment I found it convenient to have a led saddle- 

 horse at hand to ride, if requisite, rapidly from end to end, to avoid the 

 fatigue of walking through the deep loose sand. These preliminaries, inclu- 

 ding the operations of measuring the base line, were attended with so much 

 labour and difficulty, everything having to be done on an exposed beach of 

 deep sand peculiarly oppressive for walking on, and liable to frequent interrup- 

 tion from broken weather, that although commenced in July, the latter part 

 of October had arrived before they were complete ; fortunately, this month 

 is ordinarily a peculiarly fine and steady one in Ireland, and that of 184<9 

 was more than usually serene and calm ; so that our experiments, when at 

 length fairly commenced, promised well for success. 



Everything being complete and the insulating stakes for the mile of con- 

 ducting wires driven on the night of the 29th of October 1849, the following 

 results were obtained on the 30th and 31st of October and on the 2nd of 

 November 1849. 



Table No. 1. 



Date and number of experiment, and 

 time of day when made. 



Gross time shown by 

 Chronograph at ob- 

 serving end = gross 

 transit time. 

 Sharp's. 



Time shown by the 

 Chronograph at 



firing end = time of 



hang fire. 



Wheatstone's. 



No. 

 1 . 2 to 4 o'clock, Oct. 30, 1 849. 



2 



3. 3 to 5 o'clock, Oct. 31, 1849. 



4 



5. 1 2 to 2 o'clock, Nov. 2, 1 849. 



6 ' 



7 



8 large + 26 small 



8 „ + 2 jj 



+ „ 



+ 13-5 „ 



+ 9-5 „ 



+ 10-5 „ 



+ 15-5 „ 



+ 28-3 „ 



large +22-0 small 

 „ +22-5 



+ 24-0 



+ 21-5 



+ 24-0 



+22-5 



+ 21-5 



+22-0 



On the 30th of October, the time of high water in Dublin Bay was 9^* 

 49™ A.M., hence the experiments Nos. 1 and 2 were made nearly at low 



tj2 



