lie. 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



May, 



sphere, to supply air to the fire : this ohject may, however, he 

 effo<'tP(l hy making an ajierture in the front wall of the fire-place, 

 iiniiiodiately bi-hiw the fire-lmx anil f,'Tate-l)ars. 71 n, is the floor or 

 hearth of the kiln, o </, are holes, covered up in any suitable man- 

 ner, liut conunuMicatiiiir witli the asli-pit, and intended to allow of 

 tlie scoria, cinders, and clinkers heini^ removed. ;) ;), in fiff. 2, 

 sliow another manner of supplying air to the fire-places, by making 

 openings in the side walls of the same. 7 represents another mode, 

 bv which air is supplied from the atmos|)liere of tlie worksliop 

 tlirough a grating comnuinicating with tlie ash-pit. The inventor 

 remarks tliat, whatever may be the mode adopted for su])plying 

 the air to tlie fire, the same plan should be invariably adopted in 

 all the fire-places of the same kiln. 



The patentee, in conclusion, states that he is aware of coal hav- 

 ing been used for heating the kilns in which common earthen or 

 delph-ware, and even tender Knglish i)orcelain is commonly baked 

 or fired, — he does not, therefore, intend to claim the employment 

 of ])it-coal for such purposes as constituting |)art of the present 

 improvements ; but he claims. First, — the apjilication of coal for 

 heatinirthe kilns or ovens in which liard porcelain is submitted to 

 the baking or firing operation ; and, Secoinlly, — the arrangement 

 or construction of kilns or ovens, as lierein shown and described, 

 or any mere modification thereof, whereby pit-coal may be employed 

 as the fuel for heating such kilns or ovens for firing or baking hard 

 porcelain, in the place of wood, which has heretofore been employed 

 for that purpose. 



ON GEOLOGICAL CHEMISTRY. 



A lecture on " Tlie Application of Chemiral Principles to the Science 

 nf Geology" By Pi-ofessor D.^ubeny. — (Delivered at the Royal 

 Institution, Albemarle-street, March 24tli.) 



The Professor commenced his lecture with some preliminary ob- 

 servations, in which he said, he had for the last twelve months de- 

 voted liis leisure to the accumulation and study of facts in relation 

 to volcanic forces ; and having, in this pursuit, travelled a good 

 deal along the great boundary line dividing the two kingdoms of 

 geology and chemistry, he had obtained glimpses of truths, which 

 neither the pure chemist, nor the pure geologist might have had 

 the same opportunities of observing — the result being, his entire 

 acquiesence in the opinions of some of the greatest authorities of 

 the present day, that geological inquiries ought, in future, to take 

 more exclusively a chemical direction. The learned professor 

 then proceeded to allude to a subject of geological inquiry, which 

 seemed to him above all others to demand the assistance of the 

 chemist— namely, the metamorphic action which had taken place 

 between certain contiguous but dissimilar rocks — the one of erup- 

 tive, the other of sedimentary origin. A large amount of infor- 

 mation had been collected by geologists, in respect to different 

 kinds of metamorphic action, and their effects ; but as to the man- 

 ner in which these effects were produced, they would look in vain, 

 unless the chemist also were apjiealed to. One thing appeared to 

 be established — namely, that the production of mineral veins was 

 connected with the intrusion of plutonic rocks, and with the 

 changes brought about by them in the contigiuuis strata. 



Few metallic deposits occurred iu the secondary formations, and 

 even these only wlien there was dislocation w metamorphic action 

 in their neighbourhood ; while, on the other hand, metallic veins 

 were never found in modern lavas, or in volcanic products that had 

 been erupted in the open air, though several geologists had brought 

 forward facts to prove a connection between metallic matter and 

 basaltic or trappean dykes. There were various theories to ac- 

 count for the formation of mineral veins— the first supposed them 

 to l)e the result of infiltration, the water wliich percolated the 

 substance of the contiguous rocks carrying with it the several 

 mineral matters they contained, and afterwards depositing them 

 upon tlie walls of fissures caused by the contraction of the sur- 

 rounding parts ; the second supposed the materials of the vein to 

 liave been held in solution by water, but deposited in an insoluble 

 form, owing to slow- electro-chemical action ; the third hypothesis 

 assumed, that the contents of the vein, being separated from the 

 other materials hy sublimation, found tlieir way into fissures, 

 e.xisting either in other parts of it, or in the contiguous forma- 

 tions. No doubt many facts might be alleged in favour of each 

 hypothesis. In the fii'st place, granting that a given rock con- 

 tained, disseminated through it, any quantity of an oxidisable 

 metal, such as inui, copper, lead, or tin, and that tliese were al- 

 ready in combination with sulphur, the action of water and air, by 



generating sulphuric acid, would gradually give rise to soluble 

 sulphates, whiidi miglit find their way into the contiguous fissures, 

 where, owing to certain electrical or chemical reactions, tlie metals 

 would be deposited in an insoluble form. Decomposition could be 

 brought about by weak electrical currents ; and thus the second 

 hypothesis might be broim;ht in to explain what was left unac- 

 counted for by the first. Hut both presupposed the existence of 

 metallic matter in the rock from which the veinstone was derived, 

 for it was evident that these several metals could not be present, 

 in the requisite quantity, in strata deposited from water, or all 

 our mineral springs would contain traces of them, just as they did 

 of the silica and otlier substances supplied by the rock through 

 which they had been percolated. He could not, tlierefore, help 

 supposing, that tlie mineral matters, which had been confined to 

 the neighbourhood of iilutonic rocks, wei-e, in the first instance, 

 derived hy igneous agency, which constituted the machinery by 

 means of which the more uncommon metals were brought origi- 

 nally from the depths to the surface of the earth. It was re- 

 markable, however, that they were not confined to the intrusive 

 rock itself, but, in many instances, were in the metamorphic strata 

 contiguous. There was, also, evidently a connection between the 

 metallic matter in the vein and the character of the enveloping 

 rock, seemingly showing, that the ingredients of the former were 

 not sublimed directly from the interior of the globe, but had been 

 introduced from the formation in contact witli the vein. Thus 

 Fournet had stated, that at Andreasburg, in the Hartz, the veins 

 became poorer in metal when they passed from the cla}'-slate for- 

 mation into the flinty-slate; and Voltz mentioned a vein in the 

 Vosges which, in traversing successively different varieties of 

 gneiss, had its contents modified iu each. Thus, in the first va- 

 riety, which was charged with mica, the vein was small in its di- 

 mensions, and wholly destitute of metal ; in the second, which 

 had more of the character of clay-slate, it swelled out to a width 

 of 18 inches, and contained silver, combined with antimony, 

 copper, &c., together with sulphate of barytes; in the third, 

 which contained hornblende, the former were wanting, but the 

 last-mentioned ingredient continued ; while, in the fourth, which 

 was wholly destitute of mica, the silver returned for a certain 

 distance down, but was afterwards replaced by selenite, galena, and 

 sulphur, in small quantities. Sir H. de la Beche mentioned 

 similar cases in Cornwall ; and the frequency of their appearance 

 compelled the admission, that the materials of the vein were, in 

 many instances at least, dependent upon the character of the 

 rock which it traversed ; so that, supposing them deri\ed origi- 

 nally from the same igneous source, a process of segregation liad 

 subsequently taken place, by which particular bodies were deter- 

 mined to certain kinds of rock, to the abandonment of others. 



In order to pave the way to a solution of these and other diffi- 

 culties, lie submitted two questions — the first, whether igneous 

 rocks did not contain, disseminated through their substance, mi- 

 nute and, probably, infinitesimal quantities of many of those rarer 

 bodies, which were found collected together in mineral veins ? — 

 and the second, whetlier all these substances might not possess a 

 certain amount of volatility, at temperatures below their freezing 

 point, and thus become transported from place to i)lace, at periods 

 long subseipient to that at which they were originally evolve<l 

 from the interior of the earth, in a state of admixture with other 

 more abundant ingredient .'' In adopting the affirmative, with re- 

 ference to the former of these questions, it was not necessary to 

 go so far as to assume, that every basaltic dyke, m- even every 

 great volcanic f"(u-matioii, contained, as an integral part, minute 

 quantities of all the metals tliat existed in nature — for, considering 

 how infinitely small was the proportion which they bore to the en- 

 tire bulk of the crystalline igneous rocks, their absence could not 

 be safely inferred from the fact of their not having been disco- 

 vered. The facts which inclined him to suspect that they might 

 exist, were the circumstances — first, that the discovery of phos- 

 phoric acid, in so large a number of volcanic products, led to the 

 conclusion, that this body, at least, was derived from volcanic 

 emanation, and, by analogy, that metals were also so derived; se- 

 condly, the observation made by Henry Rose, that in every 

 crystalline rock traces of copper might be detected by the test of 

 sulphuretted hydrogen— tlius suggesting, that if we had any 

 equally delicate test for the other metals, they also might be as- 

 certained to be present ; and, thirdly, the fact, that not only iron, 

 arsenic, and selenium, existed amongst the products of Vesuvius, 

 but likewise lead, copper, zinc, and titanium, while tinstone also 

 was ejected by IVIiuint Etna. Now, assuming the existence of 

 metals, and other bodies of rare occurrence, amongst the matters 

 evolved from the interior of the earth by igneous processes, the 

 second hypothesis stated would enable us to account for the dilfu- 



