( 366 } 



Notes explanatory of some Passages in Professor KeilhaiCs Pa- 

 per on Granite, {^c, puhlished in Vols. xxiv. and xxv. of this 

 Journal. 



Having been favoured by our esteemed correspondent, Pro- 

 fessor Keilhau of Christiania, with some remarks on the trans- 

 lation from the Danish of his paper on the Tiaeory of Granite, 

 &c. which appeared in this Journal, vol. xxiv. p. 387, and 

 vol. xxv. p. 80 and p. 263, we subjoin a few alterations and 

 explanations, which we think will render the reasonings more 

 clear and exact. It will, of course, be necessary for our readers 

 to refer to the volumes just quoted. 



In regard to the stj-le employed in the above-men.tioned memoir, it 

 must be borne in mind, that it formed a part of the author's course of 

 lectures delivered in Christiania. It must also be clearly understood, 

 that in its first or introductory portion, that is, from page 388 (vol. xxiv.) 

 to p. 399, the author, as he himself expresses it, follows " the mode of 

 description adopted by modern geologists, or that of the volcanists," and 

 adopts their language. 



At page 389, line 20, the author intends to saj', that the thin pellicle 

 or crust of black slate is observed on the surface of the gneiss at a consi- 

 derable distance from the abrupt terminations of the strata of the slate; and 

 at the end of the same paragraph it ought to be mentioned, that the perpen- 

 dicularity of the strata is particularly remarkable in the Christiania district. 

 At p. 393, 1. G, the meaning is, that the porphyritic masses often occur 

 divided into several beds, and that by pretty horizontal joints. P. 394, 

 1. 17, read, " and sometimes that of veins, but always ivith the dimen- 

 sions of ordinary beds and veins;" and 1. 21, " traverses, for the most 

 part, the stratified masses." P. 399, I. 29, &c. " Here we have seen 

 that extraordinary disturbances in this respect have taken place. Al- 

 though the beds are not very highly inclined in the vicinity of the great 

 porphyritic districts, where, viewing the matter as Vulcanists would, the 

 melted masses must have flowed out horizontally over the strata, yet we 

 nevertheless remark, as a general rule, an elevation of the beds near the 

 granitic districts, the masses of which have, on the whole, a more or less 

 vertical position next the strata, which arc supposed to have been ele- 

 vated by this cause (P. 400, 1.5.) It is true that a high dip is a 



common phenomenon in the district; it is also true that-we onlj- find ex- 

 ceptions to this rule in localities where the strata are covered by porphy- 

 ries ; so that at all other points (where, in fact, we are always near gra- 

 nitic masses) we generally observe an inclination more or less considerable. 

 . , , . . If we glance over the geological map, and attend to the circum- 



