8G0 Memorandum of Experiments, fyc QOct. 



which a represents the battery, b the bamboo mercury cup nearly 

 full of mercury, c c the battery conductors, c c the conductors leading 

 to the explosion tube t, containing the platinum wire and priming. 



The whole cost of this apparatus, including quicksilver, is not more 

 than six rupees. 



It is obvious that many substitutes for the watch apparatus may be 

 devised, and indeed the expense of even the cheapest watch procurable 

 (ten rupees) is an objection, though an insignificant one, to its employ- 

 ment, where circumstances render it advisable to expend all the appa- 

 ratus by placing it immediately over the mine. In a remarkable set 

 of experiments which I witnessed, portfires were employed instead of 

 the watch — one, six inches in length, supported by a string the wire for 

 establishing the connexion with the battery, corresponding to the watch 

 wires a, a — a second portfire, nine inches long, supported a weight, the 

 descent of which was intended to break the connexion in the manner 

 effected by the watch wires b, b. In two of the three trials in question 

 the weight did not fall, and the consequence was the imminent dan- 

 ger of the destruction of the party whose duty it was to re-examine 

 and re-adjust the arrangements on the failure of the two first attempts. 

 In one of the trials it was observed too, that one of the tubes containing 

 the mercury was completely choked up by melted saltpetre which had 

 fallen from the portfire during its combustion. These defects seem to 

 me to constitute a most serious objection to the use of portfires; I admit, 

 however, that these are more of a military character than my contri- 

 vances—and in this, I believe, their chief merit lies. 



Explosion of the barque "Equitable." 



The barque "Equitable," bound to Sydney, and laden with wheat, rice, 

 rum, &c. while proceeding down the river in September 1839, touched on 

 Fultah Sand, and instantly turned over in six to seven fathoms water. 

 The wreck lay on her beam- ends athwart Fultah Channel, the keel to- 

 wards Calcutta. On sounding with the lead, the water over her quarter 

 shoaled to three fathoms, and then suddenly deepened to five or six. 



Capt. Fitzgerald, the engineer officer employed, determined to attempt 

 the destruction of the vessel by the explosion of 2,500 lbs. of powder 

 placed between the mizen and main masts, close to the deck. 



