Blach Sand of Cayenne. 233 



negative side of the jar. Some gunpowder being placed in 

 contact with the conductor in the cutter, and the pruning in 

 the interval of the insulated points, the jar was cliarged, and 

 the line attached to the mast head of the cutter being brought 

 into contact with the positive or inside of the jar, a discharge 

 of electric matter followed, which was passed by the line to the 

 mast head, and by the conductor through the powder to the 

 chain in the water, by which it was conveyed to the interrupted 

 communication in the boat, where it passed in the fonn of a 

 spark, and dischargmg the howitzer, returned to the negative 

 or outside of the jar by the line leading into the starboard win- 

 dow, thereby demonstrating that a quantity of electric matter 

 had been passed through tlie powder (without igniting it) in 

 contact with the mast of the cutter, sufficient to discharge the 

 howitzer. Mr. Harris then detached the communication be- 

 tween the keel of the cutter and the positive wire in the boat, 

 leaving that wire to communicate with the water only; but this 

 interru])tion did not impede or divert the charge, as the dis- 

 charge of the howitzer v/as effected with equal success as in 

 the first instance, the water forming the only conductor from 

 the cutter to the boat. In order to demonstrate that a trifling 

 Iracture or interruption in the conductor would not be impor- 

 tant, it was cut through with a saw; but this pi'oduced no ma- 

 terial injury to its conducting power. 



These trials, carried on under the disadvantages of mifa- 

 vourable weather, could not fail of convincing all present of 

 its efficacy, and called forth the decided approbation of the 

 Na^y Board in particular, which was evmced by Sir T. B. 

 Martin requesting Mr. Harris to superintend the equipment 

 of the masts of the Minden, 74, and Java frigate, preparatory 

 to its general introduction into the navy. 



BLACK SAND OF CAYENNE. 



From a paper by M. Gillet de Laumont on the black sand 

 of Cayenne, we learn: 1. Tliat this sand produces two very 

 distinct varieties of iron, one capable of attraction by the 

 loadstone, the other not: the first contains 10, the second 

 32 per cent, of oxide of titanium and a small portion of man- 

 ganese : — 2. That melted together these two varieties will give 

 good castings proper for mill-work, or will furnish, when 

 treated like other ferruginous minerals, malleable iron : — 

 3. But that it is important to set on foot experiments on a grand 

 scale on the spot, similar to those announced by M. Berthier 

 in his analysis of titanized iron of Brazil {Annales des Mines, 

 tome V. pp. 4'79 et sccj.) 



Vol. 60. No. 293. Sept. 1822. G g orni- 



