66 DE. THOMAS STERRY HUNT ON THE 



rocks must seek to couuect all the known facts of their history, by alleging a true and 

 sufficient cause for the production of their various constituent mineral species. Such a 

 hypothesis will violate no established principles in chemistry or in physics, but will show 

 itself to be in accord with them all, and will commend itself to the acceptance of those 

 who take the pains to iinderstaud it. 



The crenitic hypothesis set forth in these pages is the result of many years of patient 

 study applied to the elucidation of a great problem ; and as such is offered to chemists and 

 mineralogists as a first attempt at a rational explanation of the fundamental qiiestions 

 presented by the history of the crystalline rocks of the earth's crust. 



Contents of Sections. 



t.—Hiilcrical and Crilical.—^ 1, 2. Supposed igneous origin of crystalline rocks ; views of Lehman, Pallas, de Luc 

 and Saussure.— 3, 4. Werner's neptunian system ; his j^rimitive, transition and secondary rocks.— 5. 

 System of Hutton; his interpreter Play fair; nature of granite.— 6, 7. Indigenous, exotic and endogenous 

 rocks ; significance of eruption in geology.— 8, 9. The schools of Werner and Hutton contrasted ; their 

 unhke views of the origin of granite and of gneiss; Hutton the founder of the metamorphic school.— 10, 

 11. Hutfon's system farther defined; its analysis by Daubrée.— 12. The theological aspects of the two 

 systems. — 13- Delabeche's modified neptunian system. — 14, 15. Daubrée's later statement of the same ; 

 the intervention of internal heat.— 16. The granitic substratum of Werner adopted by Huttonians.— 17. 

 Poulett Scrope's theory of the origin of granite and of gneiss. — 18. Beroldingen and Saussure on the 

 detrital origin of gneiss; views of Boue.— 19. Lyell on the Huttonian or metamorphic hypothesis; 

 Bischof and Haidinger on pseudomorphic alteration; a metasomatic hypothesis. — 20. Naumann's criti- 

 cism of metamorphism ; the chaotic, endoplutonic, exoplutonic and thermochaotic hypotheses. — 21, 22. 

 Endoplutonism as defined by Naumann and by Hébert ; Macfarlane's statement of the endoplutonic 

 and thermochaotic hypotheses. — 24. Supposed condition of the earth's interior ; the two magmas of Bun- 

 sen ; Von Waltershausen's views. — 25. The exoplutonic or volcanic hypothesis as stated by J. D. Dana 

 in 1843.^26. Metamorphism by an incandescent ocean. — 27, 28. This view since abandoned by Dana ; 

 his statement of the metamorphic hypothesis.— 29. Clarence King on metamorphism, and the sup- 

 posed igneous origin of olivine. — 30. Kopp, Tornebohm and Reusch on the exoplutonic hypothesis. — 



31. Marr and C. H. Hitchcock on the same ; its relation to the origin and permanence of continents. — 



32. Various geologists on the supposed eruption of limestones, serpentines and iron-ores ; H. D. Rogers 

 and Belt on the igneous origin of quartz lodes.— 33. The eruptive origin of rock-salt, buhrstone and cer- 

 tain clays and sands maintained by many.— 34. Water in the formation of granites ; Sorope, Élie de 

 Beaumont andScheerer; pyrognomic minerals; liydroplutonic origin of serpentine. — 35. Excesses of 

 the exoplutonic school ; transmutation or metasomatism.— 36. ÎMotasomatosis of silicated rocks ; their 

 supposed conversion into serpentine and limestone ; King and Rowney.— 37, 38. Chrysohte rocks of 

 the Atlantic belt ; conflicting views of Genth and Julien aa to their supposed alteration (Dana's criti- 

 cisms, foot-note).— 39, 40. Metasomatosis of limestones ; views of Volger, Bischof and Pumpelly.— 41. 

 The endoplutonic, exoplutonic, metamorpliic, metasomatic, chaotic and thermochaotic hypotheses 

 summed up.— 42. The endoplutonic and exoplutonic reviewed. — 43, 44. The metamorphic, metasomatic 

 and chaotic reviewed. — 45. The thermochaotic; conditions of the problem of rock-formation. 



IL — The Dcvdopvient of a New HypoUicm. — § 47. The lines of investigation followed. — 48, 49. Order and succession 

 of crystalline rocks. — 50, 51. The hypothesis proposed in 1858 of a solid globe and a superficial layer as 

 the source of all rocks. — 52. Farther speculations in 1859 on the source of acidic and basic rocks. — 

 54. Developments in 1867-1869 ; the secondary origin of granite, and the underlying primary basic 

 stratum. — 55. The aqueous origin of many mineral silicates. — 50, 57. Geological significance of zeolites, and 

 their relations to feldspars. — 58,59. On feldspathic and granitic veins. — 60, 01. Relations of granitic veins 

 to indigenous granites and gneisses.— 62. Conclusions announced in 1879. — 63. Relations of alumina in 

 silicates to protoxyd bases. — 64. Source of granitic elements ; Scheerer, Elie de Beaumont.— 65. The 

 secondary origin of granite. — 66. Bunsen on palagonite, its origin and changes ; composition of trachytic 



