Dr. T. Sterry Hunt — On Italian Geology. 533 



oontradiction with a great number of facts. While the production 

 of chrysolite from mixtures in a state of igneous fusion is well 

 known, and while the chrysolitic rocks just mentioned are, as I have 

 endeavoured to show, the result of cr'ystallization and partial eliqua- 

 tion in a truly plutonic mass, it is not less certain that to other chryso- 

 litic rocks a neptunian origin must be assigned ; as was maintained 

 by the writer in 1879, for the so-called Iherzolite or chrysolite-rock 

 which, accompanied by enstatite, serpentine, and chromite, is inter- 

 stratified with the younger gneissic and mica-schist series in North 

 Carolina. The same may be said of the similar chrysolite rocks in 

 Norway, which, like these, are gneissic in structure and interstratified 

 in crystalline schists. In this connection I have also elsewhere 

 noted the variety of chrysolite known as glinkite, found in nodules 

 in talcose or micaceous schists in the Urals, and that purely 

 magnesian chrysolite or forsterite which occurs abundantly in 

 crystalline limestone in eastern Massachusetts. It appears evident 

 that chrysolite, like pyroxene, feldspars, spinel, and many other 

 species, is generated alike by plutonic and by neptunian agencies. 



As regards serpentine, while it may occur as a product of the 

 decay of chrysolites either of igneous or of aqueous origin, no one 

 who has intelligently studied the mode of its occurrence in grains, 

 nodules, interstratified layers and beds, sometimes hundreds of feet 

 in thickness, in the crystalline limestones and dolomites of Archgean 

 rocks alike of Laurentian and of Taconian age, and even in Palaeozoic 

 strata, can doubt the direct formation of serpentine and its accom- 

 panying silicates, in such cases, by aqueous deposition. Its separation 

 from solutions is also made apparent by the frequent occurrence of 

 veins carrying the species marmolite and chrysotile (which are but 

 crystalline forms of the same silicate as serpentine) either with or 

 without calcite, traversing ophiolitic rocks, and even, as noticed by 

 Gastaldi, in serpentinic breccias of comparatively recent date.^ 



Gastaldi had already, in 1871, expressed in general terms his 

 opinion that " all the serpentinic masses of the Tuscan and Ligurian 

 Apennines," as well as the similar rocks in Calabria, are but 

 prolongations of the great pietre verdi zone of the Alps, in which 

 he included what are known as the Apuan and the Maritime Alps. 

 To the same horizon also he referred the so-called ophitic rocks 

 of the Pyrenees. Prom my""own observations in Italy in 1881, I 

 could not doubt the correctness of these earlier generalizations of 

 Gastaldi, who however apparently did not verify his conclusions by 

 personal observations of the so-called Eocene serpentines of Liguria 

 and Tuscany until 1878, a few months before his death, when he 

 examined both of these regions with especial reference to the 

 question. His final conclusions thereon, a fortunate circumstance 

 now permits me to give to the world. 



There lies before me a letter of eleven pages, to my address, from 



1 For a detailed discussion of the questions here raised as to serpentine and related 

 silicates, see The Genesis of Serpentine, in the author's Mineral Physiology and 

 Physiography, pp. 497-509 ; also further for analyses and description o"f the 

 chrysolitic dolerite, ibid. pp. 211-213. 



