Correspondence. 893 
There is still another error in the authorit)' given for Zygofijnm Ken- 
tuckienxiis in the description to phite 40, p. 234. The species is credit- 
ed to James. It shovild have been Nettelroth. Here again Nettehoth 
described as new a species that had been described 11 years before. In 
"The Paleontologist" No. 1, July 2, 1878, p. 7, Mr. James says under 
the head of ZygoHpira modesta var. Kentuckyensis : "The fossil for 
which this name is proposed, by the finder, Henry Nettelroth, Esq., of 
Louisville, Ky." etc. Notwithstanding this we find Zygospim ken- 
tuckyensis given as a new species by Nettelroth (Kentucky Fossil Shells 
13. 1.S8) without, any reference to a previous description. In this case 
the erratum is wrong for the species is there credited to Mr. James. 
Lastly in the citation of authority for Zygospira cincinnatiensis in 
the description of plate 40, Prof. Hall gives Meek. It would be more 
correct to say "(James) Meek," for it was proposed by Mr. James and 
credited to him by Mr. Meek, in the Ohio Paleontology, (vol. I, p. 126). 
J. F.James, M. D. 
Hingham, Mass., Sept. 14, 1896. 
Geology and Mining. A highly valuable article, which illustrates 
clearly the intimate relation between mining and theoretical geology, is 
contained in the October number of the "Zeitschrift fiir praktische Ge- 
ologie," which has been published in Berlin by mining engineer Max 
Krahmann since 1893. 
Under the title "Contributions to the origin of the Freiberg lead ore 
and the Erzgebirge tin veins" are published .SG pages of valuable notes 
which were found among the papers of the late Bergrath Dr. A. W. 
Stelzner, the celebrated Freiberg geologist. They discuss the impor- 
tant question of whether the ore deposits or fissure fillings derived their 
metallic contents through leaching of the adjacent rocks or from ther- 
mal waters which ascended from great depths. 
Prof. Fridolin von Sandberger of Wiirzburg maintaineil the former 
view. He supported the "lateral secretion theory," which had already 
been advanced by him, by analyses of the mica found in the adjacent 
rocks, which mica, according to him, contains the gang metals as sili- 
cates, which are found where no leaching has taken i)lace. 
Stelzner opjjosed tliis theory and showed, in the case of the Freiberg 
gneiss, that its mica contained no metals, or, if present, that they were 
not primary silicates. Consequently the Freiberg ore deposits cannot 
have originated by leaching of the adjacent rocks. And hence also 
(and here lies the great question in practical geology) the chemical cri- 
teria proposed by Sandberger and whose application was vainly at- 
tempted at Pribram are unfortunately impossible of application at 
Freiberg and many other mining districts. This exploitation by means 
of chemistr' , that is, the drawing of conclusions from the nature and 
leached or unleached condition of the rocks, must nevertheless remain 
the hope of the miner. Genetic rehitif)nship8 between ore deposits and 
e,nclosing rocks occur on every hand. It is only a questioTi of their 
proper interpretation. 
