VIRGINIA. 475 



age. Should they hereafter be shown to be Primordial, all that Pro- 

 fessor Fontaine's evidence shows is an older series of rocks containing 

 eruptive granites, syenites, etc. His writings are far from being clear, 

 but we are unable to find any proof in them that the granite and syenite 

 are of different geological age from their associated rocks. (Am. Jour. 

 Sci., 1875, (3) IX., pp. 14-22, 93-101, 361-3G9, 416-428.) 



It would appear that Prof J. L. Campbell regards the Laurentian 

 granites and syenites of Professor Fontaine as eruptive rocks, erupted 

 since the deposition of the supposed Primordial strata, thus leaving 

 only one formation in situ under the supposed Primordial. Professor 

 Campbell holds, however, that the eruptive syenites and granites are 

 metamorphosed, and displaced underlying formations. In another lo- 

 cality he seems to regard the syenite as a " syenitic gneiss (or strati- 

 fied syenite), which might readily be taken for an igneous rock — so 

 greatly has it been metamorphosed " ; but he fails to give any evidence 

 that it is not igneous, or any reasons why it should be regarded as a 

 metamorphosed sedimentary rock. He also fails to show that the sup- 

 posed Primordial is composed of the debris of his supposed Archsean. 

 As has been before remarked in other similar cases, it is not here our 

 intention to assume that the conditions are not as they are assumed to 

 be ; it is simply our wish to call the attention of the observers to the 

 fact that their published observations fail to furnish the proof necessary 

 to be presented before these ideas can be accepted as axioms. They 

 are not of the nature of self-evident truths. (Am. Jour. Sci., 1879, 

 (3) XVIIL, pp. 16-29, 119-128, 435-445.) 



The latest setting forth of Professor Fontaine's views on the subject 

 here under discussion will be found in a letter from himself to Professor 

 Lesley, dated January 20th, 1883. (Second Geological Survey of 

 Pennsylvania, Report, C*, 1883, pp. xiii.-xvi.) In this letter he clearly 

 assumes that the division of the Azoic rocks into Laurentian and 

 Huronian is to be taken for granted as something so clearly established 

 that it must stand, no matter how difficult it may be to reconcile the 

 theory with the facts. The Huronian seems to be wanting ; that is, he 

 finds it very difficult to discover rocks having the proper lithological 

 characters. Thus he says (/. c, p. xiii.) : — 



" The Blue Ridge in the northern part of Virginia is, as I take it, much as 

 it is in your South Mountains of York, &c. The Huronian strata hide very 

 largely the Laurentian. On the Potomac the latter does not show at all. 

 .... The Laurentian sinks and expands as we go south in Virginia, and 

 often has over it a mere remnant of the Huronian Still farther south- 



