Dr, J. Szabo — On Determining Felspars in Bocks. 223 



earth's crust, producing what he termed a " primary structure," and 

 "showing the effect of a polar crystallizing force" (Quart. Journ. 

 Geol. Soc. vol. vi. p. 364), were certainly analogous to, if not iden- 

 tical with Dr. King's world-wide magnetic action producing meri- 

 dional and other joints. Mr. Evan Hopkins' hypothesis of " cleavage- 

 planes," however, was associated with many untenable views ; and 

 certainly did not tend to elucidate the geological structure of either 

 South America or South Australia, to which he applied it. On the 

 contrary, the folded and crushed strata, cleaved by lateral pressure, 

 and showing their obscured bedding-planes only to the instructed 

 geologist, were unravelled on the mechanical hypothesis of cleavage 

 alone. So in other countries also ; and if this theory be sufficient 

 for such great results, why should we ask for the intervention of an 

 additional divisional structure, of universal range and of enigmatical 

 origin ? Dr. King's reply would probably be — at least to account 

 for the above-mentioned cases of imperfect, secondary, and inter- 

 calated cleavage-sets, and for some discrepancies in the strike of 

 bedding and cleavage. Good ! Jointing is not an uncommon phe- 

 nomenon, and it must have often been modified by pressure ; and 

 hence the explanation, now offered by our author, of some or all of 

 these peculiar stratal conditions. But, as the jointings or other 

 divisional structures, without pressure, will not explain the squeezed, 

 contorted, or elongated conditions of fossils, the parallelized arrange- 

 ment of particles, and the crumpling of seams, in cleaved rocks, the 

 meclianical theory must be accepted, we believe, in most cases, over 

 vast areas of the earth's crust. T. K. J. 



II. — On a new Method of determining the Felspaes contained 

 IN EocKs. By Dr. J. Szabo, Professor of Mineralogy and Geology 

 in the University of Buda-Pesth, Hungary ; Corr. Memb. Geol. 

 Soc. With 11 Woodcuts and 5 Coloured Plates, pp. 88. (Ger- 

 man edition, 1876.) 

 rflHIS method is based on those flame-reactions, for the first 

 J_ description of which science is indebted to Bunsen's classical 

 papers, entitled " Lothrohrversuche," and " Flammenreactionen," 

 published in Poggendorf's Annalen in the years 1859 and 1866. 



The author of the present Memoir has found it necessary to 

 establish a more precise means for determining the fusibility of the 

 non-metallic minerals in general, and especially of the felspars ; and 

 he finds that at the same time all the other characters necessary for 

 the exact determination of the species of felspar can also be observed 

 in the flame. 



The whole method is exhibited in a series of tables, in which the 

 degrees of fusibility, the peculiar characteristics of the fused products, 

 and the soda and potash reactions of the different species and varieties 

 of the felspar family are very clearly exhibited. 



In carrying out this method for determining the species of a felspar, 

 a fragment of the size of a grain of mustard-seed is held in a loop of 

 platinum wire and subjected to the three following experiments. 1. 



