RESEARCHES IN THERMAL METAMORPHISM. 201 



green spinel, and especially hornblende are locally abundant, 

 and sometimes little crystals of blue tourmaline, an unex- 

 pected mineral. 



Among other examples we may mention the case, also 

 described by Lacroix, of the Ordovician limestones meta- 

 morphosed by the elseolite-syenite of Montreal (18). The 

 limestones become thoroughly crystalline, and their contact 

 with the intrusive rock is marked sometimes by a zone of 

 garnet or cancrinite, sometimes by a granular aggregate of 

 pyroxene, garnet, and wollastonite. The intensity of the 

 metamorphism and the relative proportions of the several 

 minerals formed vary greatly in short distances. There are 

 often patches consisting exclusively of granular silicates, 

 wollastonite, pyroxene, and garnet, sometimes accompanied 

 by felspar and perofskite, intimately associated with the 

 garnet. Here the coming in of such minerals as cancrinite 

 and perofskite (the latter also found near the elseolite- 

 syenites of Arkansas) seems to suggest some degree of 

 connection between the products of metamorphism and the 

 nature of the igneous rock that produced it, which bears on 

 one of the more obscure problems of our subject. 



BIBLIOGRAPHY. 



PART I. 



(1) GARDINER, Miss M. I. Contact-Alteration near New Gallo- 



way. Quart. Jour. Geol. Soc., vol. xlvi., pp. 569-580, 1890. 



(2) Barrow, George. On an Intrusion of Muscovite-biotite 



Gneiss in the South-eastern Highlands of Scotland, and its 

 accompanying Metamorphism. Quart. Jour. Geol. Soc, vol. 

 xlix, pp. 330-356, 1893. 



(3) Harker, Alfred, and Marr, J. E. The Shap Granite and 



the Associated Igneous and Metamorphic Rocks. Quart. 

 Jour. Geol. Soc., vol. xlvii., pp. 266-327, 1891. Supplement- 

 ary Notes on the Metamorphic Rocks around the Shap 

 Granite. Ibid., vol. xlix., pp. 359-371, 1893. 



(4) Sauer, A. Erlaiitcrungen zur geologischen Specialkarte des 



K'dnigreichs Sachsen. Section Meissen, Blatt 48, 1889. 



(5) DALMER, K. Ibid. Section Tanneberg, Blatt 64, 1888. 



(6) Beck, Richard. Ibid. Section Berggiesshiibel, 1889; Sec- 



tion Pirna, 1892 ; Section Kreischa-Hanichen, 1892. Also, 



