190 



THE CniL ENGINEER AND ARCHITECrS JOURNAL 



LJuNt, 



;icti(Mi, siicli (liffi'i-encps woiild be sufficient tii iiroilnci' inirreiits. 



Tliat wiis iiinl"u1)ti.HlIy the case in tallio and (i'nnl nin<lurtini; 



bodies, l)ut no siicIi result liad been olitained from eripcriments on 

 granite, slate, or irreenstone. 



FA series of experiments was here introduced — and. notwitn- 

 standinix the use of an active tjalvanic series, it was shown that 

 the voltaic current would not transverse eitlier pranite, slate, 

 elvaii, or irreenstone — connection hehit; made with tliem and a very 

 delicate ffalvanometer, ni>on which not the sliglitest indication of 

 any action on the needles could be obscr\'ed.] 



Ariien moist, tlicse rocks became over tlieir surfaces conductors ; 

 and. by this means, the action on a sinf,'le i)air of zinc and coi)per 

 plates, not more than an inch square, was detected throu.'j:li a con- 

 siderable extent of country. Mr. W. J. Ilenwood liad supposed 

 that he had detected currents of voltaic electricity throuirli the 

 aranite and slate rocks of Cornwall ; but the lecturer, wlio had 

 repeated those experiments with p-eat care, was led to believe tliat 

 the slight deflection of the needle ol>tained was due entirely to 

 some chemical action in the wires employed at the point of con- 

 tact with the rock, or within its lenstli— such slight disturbances 

 beinir of constant occurrence in all experiments of tliis class. 

 Althoufrh tliere was not. therefore, any experimental evidence in 

 proof of the vcdtaic condition of the rocks, yet the regularity of 

 arrangement oliserved in the lodes themselves — in wliich zinc, 

 copper and quartz, lime, pyrites, l)arytes, fluor-spar, iirgentiferous 

 lead, and ijuartz, alternated in the most legular order, as was 

 shown by s])ecimens from tlie mines of Cornwall, Derbyshire, 

 Saxonv. and Mexico — present features so analogous to those which 

 often a])pear in galvanic experiments, that we are compelled cer- 

 tainly to infer that some modiflcation of the electric force was 

 concerned in the ])henomena. Specimens of pseudo-morphous 

 bodies from the Cornish mines, and arrangements of brown spar 

 upon quartz, from Pcliemnitz, tpiartz upon fluor-spar, and iron 

 pyrites, and the doul)le sulphuret of copper u])on large quartz 

 crystals, in all of wliich a uniform system of arrangement, per- 

 fectly independent of each other, was shown — and these were to 

 be referred, in all jirobability, to the disposing power of electrical 

 currents. 



Such were the principal evidences to be adduced in support of 

 the electrical theory. Mr. R. W. Fox was the first to discover any 

 indications of electricity in mineral lodes. By placing copper 

 wires against two portions of a lode, or of two lodes divided by a 

 cross-course, and connecting those wires with a gah-anometer, a 

 considerable deflection of the needle was obtained — often to such 

 an extent, that from the violence of the action, it was impossible 

 to note the deflection. In nearly all the mineral lodes of Corn- 

 wall, upon whicli experiments were made, these currents liad been 

 detected. Ex|)eriments made by Mr. Fox, in Coldberry and 

 Skeers, in Teesdale, gave, however, negative results ; and the 

 results on the lead lodes at tlie Mold mines were not very decided. 

 Prof. Reich, of Freyburg, obtained very decided results upon the 

 lead and silver lodes of that district ; and, in one case, succeeded 

 in detecting a mass of silver ore at some distance behind the rock. 

 Von Stromlieck, on the contrary, c(uild obtain lui results from the 

 lead and copper lodes on the riglit bank of the llhine. In addi- 

 tion to these results, others of a most satisfactory kind had been 

 obtained by Mr. Henwood and Mr. Jcdin Artliur Phillips. Tlie 

 lecturer had himself almost invariably obtained very decided 

 ^alvanometric indications from tlie copper lodes of Dolcoath, East 

 Wheal Crofty, East Pool, and other Coi-nish mines — in one instance 

 so powerfully, that the electro-chemical decomposition was pro- 

 duced. Mr. Fox has been successful in procuring an electrotype 

 copy of an engraved plate by the current collected from two lodes 

 of iron and of copper pyrites, and also in inducing magnetism in 

 a liar of soft iron. Mr. Pattinson, at the w ish of tlie British Asso- 

 ciation, made a series of experiments on the rocks of the limestone 

 formation in the lead districts of the Jiortb ; bnt he could not 

 detect any evidence of electrical currents. 



It now became a ipiestioii, to ascertain if these currents of elec- 

 tricity, detected in mineral lodes, were in any way connected with 

 the general currents traversing tlie eartli, according to the theory 

 of Amjiere ; or, were they of a more local character ? The lecturer 

 was induced to conclude, from all his experiments and observations, 

 that these currents were entirely local, and due to the cliemieal 

 action going on within the lode itself. In all cases where chemical 

 action could be detected, it was certain the current acting on the 

 galvanometer was more energetic than where no chemical change 

 was apparent. In this way miglit be accounted for tlie failure of 

 Von Strombeck on the lead and copper lodes of the Rhine, and of 

 Mr. R. W. Fox himself on the lodes of Teesdale — in all probability, 

 those lodes being in a very permanent condition. It was thought 



by the lecturer that the fact, that these currents often being found 

 to traverse tlie lodes in a direction contrary to the currents of 

 Ampere, and freipieiitly at riglit angles to them, militated against 

 tliat view whicli referred the one to tlie influence of the other. The 

 lecturer had also detected currents fnun ])iles of ore on the surface, 

 which had been ex]iosed to the influences of the atmosphere; and 

 these currents were certainly only measurers of the amount of 

 chemical action going on in the pile. 



That these local lode currents might have a powerful effect upon 

 masses of matter exposed to their influences, was highly probable ; 

 and he was disposed to refer the conditions in which cobalt and 

 nickel were often found in tlie cross-courses, between the ends of 

 dislocated lodes, as due to this local chemical electricity. Tlie 

 character of many of the decomposing lodes was next described; 

 and it was shown that, under the influence of the percolatiini of 

 rain-^iater from the surface, charged m ith oxygen, and the action 

 of the saline water risiiiif from below, few lodes admitting water to 

 flow through them cmild be free from chemical action. He had 

 analysed the waters of many of the deep mines, and the following 

 were the results (jf a few of these analj'ses : — 



The water from (ireat St. George contained, in a cubic foot, 590 

 grains of common salt ; that of the United Mines, rising hot, -1.81 

 grains; of Dolcoath, 218 grains; of Great M'heal Charles, 612 

 grains ; Consolidated !Mines, at 80 fathoms, 656 grains ; and at the 

 'i50 fathom level, 918 grains. This muriate of soda was estimated 

 quite independently of the earthy and mineral salts. It was, 

 doubtless, derived by infiltration from the ocean ; and, from its 

 (juantity, acted, no doubt, powerfully upon the lodes it traversed. 



Altliougb these currents, detected by the galvanometer, were not 

 regarded by the lecturer as in any way j)ro\ing electrical agency 

 in the formation of mineral veins, yet the evidence obtained by 

 Mr. Fox, by i\Ir. Jordan, and more recently by himself, that elec- 

 tricity would gi\e to clay a schistose structure and form along a 

 curved line, no doubt related to some line of electrical action, a 

 miniature lode of co])per (of which illustrations were exhibited), 

 siip])orted the general view of electrical action. Incidentally, the 

 conducting powers of iron and copper jiyrites, galena, and some 

 other minerals, ;vere experimentally shown ; and also the decom- 

 position of yellow ore by electrical action. 



In conclusion, the lecturer carefully recapitulated all the maia 

 points of evidence, for and against the electrical views, and pointed 

 out many I'ery curious circumstances, evidently dependent upon 

 some peculiar conditions of the adjacent rocks, but which could 

 not he referred, -vvith any certainty, to electrical action. Probably, 

 those currents now nearly determined as in constant flow around 

 the earth, might produce the curious results observed ; but a far 

 larger amount of experimental ex'idence than that yet obtained 

 was required, before this view could be admitted as one of the 

 received facts of inductive science. 



NOTES OF THE MONTH. 



Baron de GohUmid's House. — The grand ball-room at St. John's Lodge 

 in the Regent's Park, of wliich so much lias been spoken and written, was 

 lighted last week, for a party given by the Baron de Goldsmid. The effect 

 is reported to have been most admirable. Although ilr. Barry and Mr. 

 Poynter had exerted every care, the eti'oct of light upon the decorations 

 must have caused them some anxiety, and it must be most gratifying to 

 thera to have succeeded so completely. The richness of the gilding contri- 

 butes to the grandeur of the room, without destroying its air of cliasteness; 

 and if Mr. Barry be reproached that there is a want of repose in the House 

 of Lords, and too great profusion of ornamentation, the same ohjection can- 

 not be made against a hall-room. Tliis saloon is the great work of the 

 present season, and it is pleasing to learn that the munificent patronage of 

 the Baron de Goldsmid has been, as usual with him, displayed in the encou- 

 ragement of English artists, instead of being lavished upon foreigners, as is 

 too common with our nobility. 



Mineral Produce of Austria. — The latest published government accounts 

 give the following as the mineral produce of Austria : — Gold, 35 cwt. ; silver, 

 547 cwt.; mercury, lOG^ tons; iron, 148,379 tons; copper, 2,753 tons; 

 lead, G,6G0 tons; litliarge, 1,299 tons; zinc, 227 tons; calamine, 908 tons; 

 tin, 49 tons; antimony, 231 tons; cobalt, 132 tons ; manganese, CJ tons ; 

 arsenic, 50 tons; plumbago, 1,327 tons; alum, 1,494 tons; sulphate of 

 iron, 5,354 tons; sulphate of copper, 288 tons ; sulphur, 1,259 tons; coal, 

 524 tons. 



The Hohjhead Steam-Pachets. — The principal trial of the new Holyhead 

 steam-packet LieweUijn, master. Commander Grey — vessel and engines de- 

 signed and manufactured by Miller, Ravenhill, and Co., of Blackwall — took 

 place on Monday, the 15th ult. It is stated that, under adverse circum- 

 stances, she made four uns at the measured mile, at Long Reach, which 



