AMERICAN NATURAL HISTORY. 



Foster (J. W.) and Whitney (J. D.). On the age of the sand- 

 stone of lake Superior : with a description of the phenome- 

 na of the association of igneous rocks. — Proc. Amer. Assoc. 

 Adv. Sc. v. 1851, 22. (36 



Foster (J. W.) and Whitney (J. D.). Notice of the Report of the 

 geology and topography of a portion of the lake Superior 

 land district.— Amer. Journ. of Sc. XII. 1851, 222. (37 



Foster (J. W.) and Whitney (J. D.). On the different systems of 

 elevation which have given configuration to North America; 

 with an attempt to identify them with those of Europe. — 

 Proc. Amer. Assoc. Adv. Sc. v. 1851, 130. (38 



Foster (J. W.) and Whitney (J. D.). Report on the geology and 

 topography of a portion of the lake Superior land district, 

 in the state of Michigan. (Ex. Doc. No. 69, 31st Cong, 

 1st session). Washington. 8vo. 1851. With plates and 

 maps. (39 



GrREWlNGK (C). Beitrag zur Kenntniss der Orographischen und 

 Geognostischen Beschaffenheit der nord-west Kiiste Ameri- 

 ca's, mit den anliegenden Inseln. pp. 351, large 8vo. St 

 Petersburg, 1850. With five maps and four lithographic 

 plates of fossils. (40 



Hale (C. S ). Observations on the gnathodon beds around the head 

 of Mobile Bay.— Amer. Jour, of Sc. XI, 1851, 164. (41 



Hayes (A. A.). On Rhode Island coal. — Amer. Journ of Sc. xi. 



1851, 267. (42 



Hough (Franklin B.). On the cylindrical structure observed in 

 Potsdam sandstone. — 'Proc. Amer. Assoc, Adv. Sc. IV. 

 1851, 352. r43 



Hunt (T. S.). On the taconic system. — Proc. Amer- Assoc. Adv 

 Sc. iv- 1851, 202. (44 



