538 



METALLURGY. 



each other, and are contained in circular cas- 

 ings of wrotight-iron, or steel plates riveted 

 together. The regenerators are also separate, 

 one from the other. The arrangement con- 

 sists of a circular furnace body placed on a 

 platform supported by girders, while the re- 

 generative chambers are placed in pairs at 

 each end of the furnace. The furnace is thus 

 left entirely clear underneath. 



Origin of Ores. Concerning the origin and 

 manner of deposition of ores, Prof, von Grod- 

 dek, of Austria, and Dr. Sandberger, attribute 

 the- tilling of veins to the exudations of mineral 

 secretions from the wall-rocks, or to lateral 

 secretions. Mr. S. F. Emmons, who has stud- 

 ied the deposits at Leadville, and Mr. G. F. 

 Becker, who has examined those of the Corn- 

 stock lode, credit the ores to the leaching of 

 the igneous rocks. Prof. J. S. N ewberry holds 

 with Richthofen, that the ores mainly origi- 

 nated from below, and supports his view with 

 illustrations from well-known American mines, 

 going to show that neither of the other two 

 theories can prevail. He admits lateral secre- 

 tion as a contributory agency, saying : " It is 

 certain that the nature of the deposit made in 

 the fissure has frequently been influenced by 

 the nature of the adjacent rock. Numerous 

 cases may be cited where the ores have in- 

 creased or decreased in quantity and richness, 

 and have otherwise changed character, in pass- 

 ing from one formation to another; but even 

 here the proof is generally wanting that the 

 vein materials have been furnished by the 

 wall-rocks opposite the places where they are 

 found." Thus the quartz in the veins of the 

 Star district of southern Utah could hardly 

 have come from any other source than " from 

 silica-bearing hot waters that flowed up along 

 the side of the trap, depositing there, as in the 

 numerous and varied veins of the vicinity, 

 mineral matters brought from a zone of solu- 

 tion far below. . . The results of all recent as 

 well as earlier observations have been to con- 

 vince me that Richthofen's theory of the filling 

 of the Comstock lode is the true one, and that 

 the example and demonstration of the forma- 

 tion of mineral veins, furnished by the Steam- 

 boat Springs is not only satisfactory but typi- 

 cal." 



Electric Conductivity of Metals and their Alloys 

 M. Lazare Weiler, in a paper read before the 

 Socie'te' Internationale des Electriciens, gives 

 the conductivities of different metals, as com- 

 pared with silver and pure copper, as follow : 



Speaking of the conductivity of alloys, M. 

 "Weiler thus decides an important mooted 

 point : " It should be remarked," he says, 

 " that it is not true, though sometimes assert- 

 ed, that in an alloy the electric conductivity is 

 always lower than that of the poorest conduct- 

 or of constituents. It is simply demonstrated 

 that the union of two bodies modifies to a 

 great extent their separate conductivities, and 

 this fact ought certainly to lead sometimes to 

 interesting results." 



Miscellaneous* Dr. Strohecker, of Frankfort, 

 found that the clay in the neighborhood of 

 Hainstadt, near Seeligenstadt, contains consid- 

 erable proportions of some of the rare metals, 

 particularly of cerium. Picked samples of the 

 two upper layers of the clay gave 13*42 per 

 cent, of cerium hydroxide in the flesh-colored 

 and cinnamon-brown clay of the upper layer, 

 and 9-40 per cent, in the darkish-gray clay of 

 the second layer. The variations in color are 

 supposed to depend upon diversities in the 

 properties of the cerium hydroxide. The 

 bricks made from the clay of the upper layer 

 vary in color, according to the temperature at 

 which they are burned,* the lightly burned 

 bricks having an orange-yellow color, while 

 those burned at a white-heat are leather-col- 

 ored, and have a silver-gray appearance. A 

 variety of the second layer, which is black 

 from the presence of lignite, yields lemon-yel- 

 low bricks, through the conversion of the ceri 

 um oxide Ce 2 O 3 into the lower oxide Ce 3 

 by the action of the carbon which is preseu 

 The blackish-gray variety of the clay yie " 

 orange-red to orange-yellow bricks. A thi 

 layer of the clay contains less cerium than t 

 other two, and the bricks made from it are 

 a fainter orange-color. The amount of gluci 

 present is characteristic of the Hainstadt clay. 

 Ammonium chloride, which occurs only in 

 traces in some portions of the clay, exists in 

 quantity in others. It appears from these 

 analyses that the oxides of cerium, which have 

 hitherto been regarded as of only theoretical 

 interest, have a technical importance. They 

 have long served as coloring substances in 

 building-materials, without the fact having 

 been known ; and, from the large amount pres- 

 ent in the Hainstadt clay, there are prospects 

 of their being brought into use as paints. The 

 small amount of iron present in the clay (Fe 8 s 

 0-919 to 0-6356) was found to have no influ- 

 ence on the color of the bricks, which, how- 

 ever, was affected by the admixture of larger 

 quantities of iron. The somewhat remarkable 





