214 DR. THOMAS STERRY HUNT ON THE 
newer gneisses and mica-schists, and the still younger lustrous schists, corresponding 
respectively to the Laurentian, Huronian, Montalban and Taconian of North America ; the 
second and third of these being the Pebidian and the Grampian of Great Britain. * Ser- 
pentines, it was shown, occur in the Alps interstratified in the second, third and fourth 
of these groups, the youngest of which includes the marbles of Carrara. 
6. The view that this youngest group is mesozoic, is discussed, and the relations of all 
these groups of crystalline schists to the fossiliferous rocks of the mainland, and of those of 
Elba and Sardinia, are set forth, showing their pre-Cambrian age ; while it is maintained 
that the ophiolites and other crystalline rocks which have there been referred to the 
tertiary are but exposed portions of these pre-Cambrian rocks. 
7. The crystalline rocks of the Simplon and the St. Gothard, and those of Saxony and 
Bayaria, are considered and are compared with the younger gneisses of North America. 
8. The relations of the so-called tertiary serpentines to the surrounding strata are 
elucidated by a detailed discussion of the mass of Monteferrato, in Tuscany, which is 
regarded as of pre-Cambrian or eozoic age. ; 
9. The various theories proposed to explain the genesis of serpentines are considered, 
and that of their aqueous origin is adopted. 
10. The geognostical history of olivine is discussed, and the essentially neptunian 
origin of many olivine-rocks, is maintained. 
11. The contradictory views as to the’ geognostical relations of serpentine are consi- 
dered, and an attempt is made to show that the appearances of intrusion, upon which 
some have insisted, are explained by subsequent movements of the strata in which the 
serpentines are included. 
CONTENTS OF SECTIONS. 
I.—Historical Introduction —? 1. Are serpentine rocks indigenous or exotic? 2-5. Conflicting views of European 
geologists; 6-7. Of American geologists ; $8. The Canadian geological survey ; 9. The genesis of crystalline 
rocks in general; 10. Supposed metasomatic origin of serpentines; 11-12. Theory of the aqueous origin of 
serpentines and of eruptive rocks ; 13-I4. Aqueous formation of magnesian silicates ; 15. A great problem 
in chemical geology. 
II.—Serpentines of North America.—?.16. Laurentian serpentines; 17. Huronian serpentines; 18-20. Serpentines 
of Pennsylvania; 21-24. Serpentines of Manhattan and Staten Islands, Hoboken and New Rochelle; 
25-26. Serpentines in the Taconian; 27-34. Serpentines in the Silurian at Syracuse, New York ; description 
and analysis ; 35. Sepiolite and other magnesian silicates accompanying gypsum. 
TIL.—Serpentines of Europe.—? 36-38. Bonney on the serpentine of Cornwall; 39-40. The names of ophiolite, 
gabbro, euphotide, etc.; 41-42. Bonney on Italian serpentines; 43-45. Serpentines at the geological 

* It remains to be seen whether the Arvonian series, which is essentially composed of stratified halleflinta or 
petrosilex-rocks, passing into quartziferous porphyries, and is largely developed at the base of the Huronian in 
parts of North America, and of Great Britain, is not represented in the Alps. Since we haye seen the serpentines, 
lherzolites, euphotides, diabases, and even the marbles of the Alps and other regions, removed from the category 
of eruptive mesozoic and cenozoic masses, and shown to be regularly interbedded members of pre-Cambrian strati- 
fied series, it is, I think, a legitimate subject for inquiry whether the quartziferous porphyries. which are so 
largely developed at Botzen, and elsewhere in the Alps, and have been regarded as eruptive rocks of Permian age, 
may not prove to belong to a stratified series, the equivalent of the Arvonian, with which, to judge from descriptions, 
analyses and specimens, they bear a close resemblance. For an account of these rocks of Botzen by one who 
regards them as plutonic, see Judd in the Geological Magazine for 1876, vol. xiii., pp. 200-214, and for details with 
regard to the history of the Arvonian series,see the author in 1880, American Jour. Science, [3]. (xix. pp. 274,278, et seq.) 

