lii PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



tion of oxide of aluminium (Corundum) and fluoride of boron. Simi- 

 l&x^j ruby, sapphire, staurotide, and other aluminous minerals have 

 been produced ; and it is conceivable that this kiad of action by 

 sublimation may have had influence in the filluig of mineral veins.* 



If carbonate of lime be soaked in chloride of magnesium, and ex- 

 posed to a moderate heat (100°-200° C), the salts are partially de- 

 composed, and a part of the lime is replaced by magnesia. If the 

 chloride of calcium which is formed in the process be removed, and 

 fresh chloride of magnesium be added, a second dose of magnesia re- 

 places a second part of the lime, and forms dolomite. Sulphate of 

 magnesia will have an analogous eifect. If clay and chloride of 

 sodium be employed instead of carbonate of lime and chloride of 

 magnesium, a silicate of soda may result ; and by varying the pro- 

 cess, other proofs may be gathered of the generation of minerals 

 under aqueous action heightened by heat. 



The ingenious researches of M. Alphonse Gages, who by means of 

 partial solution of several minerals has shown them to be compounds 

 in which metamorphosis has been partially carried out, so that a 

 skeleton of one mineral lies concealed in the substance of another t, 

 appear to deserve the special attention of mineralogists, who by 

 means of the modern microscope and polarized light have at their 

 command powers of investigation unknown to Werner and Jameson, 

 De L'Isle and Haiiy, Cronstedt and Linnaeus, and only partially 

 employed by Mohs and JSTaumann and the great writers of Germany. 



The labours of M. Delesse on the great subject of the metamor- 

 phism of rocks have already drawn forth the praises of my pre- 

 decessor, himself one of the earhest and ablest of the inquirers into 

 the changes which the elder strata of the earth have expeiienced by 

 the action of known and probable causes J. The recent publication, 

 in a complete form, of the series of researches for which we are 

 indebted to M. Delesse, has placed in the hands of geologists a 

 summary at once clear, full, and precise, of the principal facts which 

 have been recorded by eye-witnesses of the apparent effect of granitic 

 and doleritic masses, dykes, and veins, on strata of various kinds in 

 contact with them — carbonaceous, calcareous, arenaceous, argilla- 

 ceous, ferruginous. The numerous examples of this local metamor- 



* Geologist, Nov. 1858. Dr. Phipson's communications to this publication 

 furnish many valuable and interesting notions of the progress of Continental 

 geology. 



t Thus in the fibrous dolomite of Miask (Ural) an asbestiform skeleton of 

 magnesian tremolite may be detached by means of diluted hydrochloric acid ; 

 and in the magnesite which borders a dyke of trap where it passes through chalk, 

 near Maghera, the same process discloses a skeleton of pure silica lighter than 

 water. Serpentine cut in thin slices, and treated with acid, discloses the sub- 

 stances of which it is composed, leaving always, however, a siUceous skeleton — 

 an evidence of its metamorphic origin. (Communications to the Geol. Soc. of 

 Dublin and the Brit. Assoc. 1858.) 



I The chapter on Igneous and Metamorphic Eocks which enriches the Eeport 

 of General Portlock, on Londonderry, Tyrone, and Fermanagh, could have been 

 written in no other country than Ireland, and by no other hand than that of our 

 late President. Dated in 1843, it is full of facts and ideas of the highest geo- 

 logical interest, the fruit of many years of reflection and research. 



