772 APPENDIX. 



3. Unconformability. — Never confound the unconformity that is connected with a 

 fault with true unconformability, due to unconformable superposition. The different, 

 and differently-dipping, rocks on the opposite sides of a fault of a thousand feet or 

 more may belong to the same period. 



Never assert with positiveness that unconformability exists, unless the fact is dis- 

 tinctly visible in an actual section showing the contact of beds of unlike dip ; for the 

 unlike dip in different rocks, if observed at points only a hundred feet apart, may be 

 owing to a bend in one or the other stratum in that interval, or to displacement. 



Observe the distinction between overlap (p. 101), and unconformability due to deposi- 

 tion on upturned strata. 



4. Metamorphic Rocks. — Study regions of metamorphic or granitoid rocks in pre- 

 cisely the same manner as those of ordinary stratified rocks, whether they be Archaean 

 or of later origin, making no use of lithology except in order to follow a series of 

 rocks from mile to mile over a country, and always relying implicitly on stratigraphy. 

 Remember also that a layer of quartzite may be gneiss or mica schist a few rods off; 

 and that the same crystalline rocks, with a rare exception, may belong to formations of 

 very various geological ages. 



As to granyte, syenyte, and dioryte, leave to the infancy of geology the notion that 

 they are primitive rocks, and make their age, in each case, a question to be solved by 

 careful stratigraphical investigation. In connection with the investigation the following 

 questions are to be answered: Is the rock eruptive granyte, syenyte, or dioryte? Is the 

 rock a vein formation V Or, is the rock part of the metamorphic series of a region, as 

 proved by its mode of association with metamorphic rocks, and its gradation into gneiss- 

 oid granyte and gneiss, or into any other schistose crystalline rock V a fact with much 

 the larger part of the granyte, syenyte, and dio^te of the world. The kinds of crys- 

 talline rocks that are most characteristic of the Archaean terranes are mentioned on 

 page 151. 



B. — Catalogue of American Localities of Fossils. 



The following catalogue contains some of the more important of American localities 

 of fossils, and is intended for the convenience especialty of the student-collector. 



Localities of Fossils. 



Acadian Group. — Coldbrook, Ratcliffe's Millstream, St. John, N. B. ; Long Arm of 

 Canada Bay, Newfoundland. 



Potsdam Group. — Swanton, Vt.; Braintree, Mass.; Keeseville (at "High Bridge"), 

 Alexandria, Troy, N. Y. ; Chiques Ridge, Pa. ; Falls of St. Croix. Osceola Mills, Trem- 

 paleau, Wisconsin; Lansing, Iowa; St. Ann's, Isle Perrot, C. W. ; near Beauharnois 

 on Lake St. Louis, C. E. 



Calciferom. — Mingan Islands, St. Timothy, and near Beauharnois, C. E. ; Grand 

 Trunk Railway between Brockville and Prescott, St. Ann's, Isle Perrot, C. W. ; Am- 

 sterdam, Fort Plain, Canajoharie, Chazy, Lafargeville, Ogdensburg, N. Y. 



Quebec Group. — Mingan Islands, Point Levi, Philipsburg, and near Beauharnois, 

 C. E. ; Point Rich, Cow Head, Newfoundland; cuts in Black Oak Ridge and Copper 

 Ridge, Knoxville and Ohio Railroad, Tenn.; Malade City, Idaho. 



Chazy Limestone. — Chazy, Galway, Westport, N. Y. ; one to three miles north of 

 "the Mountain," Island of Montreal, C. E. ; St. Joseph's Island, Sault Ste. Marie, C. 

 W. ; Knoxville, Lenoir's, Bull's Gap, Kingsport, Tenn. 



Bird's-eye Limestone. — Amsterdam, Little Falls, Fort Plain, Adams, Watertown, 

 N. Y. 



Black River Limestone. — Watertown, N. Y. ; Ottawa, C. W. ; Island of Montreal, and 

 near Quebec, C. E. 



Trenton Limestone. — Adams, Watertown, Boonville, Turin, Jacksonburg, Little 

 Falls, Lowville, Middleville, Fort Plain, Trenton Falls, N. Y. ; Pine Grove, Aaronsburg, 

 Potter's Fort, Milligan's Cove, Pa.; Highgate Springs, Vt. ; Montmorency Falls and 



