On the Boulders of Primitive Rocks found hi Ohio, fyc. 29 i 



give them specific names, viz. Orbiculatus, Phaseolus, and 

 Foliatus, of the Unios ; and Undulata, of the genus Anodon- 

 ta — my other descriptions are generally copied from Mr. 

 Barnes, except in particulars where my specimens differed 

 from his. The subject is in a manner new to me, and lacks 

 the finish of an experienced workman. 



Art. VIII. — On the Boulders of Primitive Rocks found in 

 Ohio, and other western states and territories ; by Benja- 

 min Tappan. 



to the editor. 



It seems to have been taken for granted, that the masses 

 of primitive and transition rocks, found in the territory north 

 west of the Ohio river, scattered over the surface of the 

 ground, and occasionally beneath the surface, as deep as ex- 

 cavations have been made, are of foreign origin. Found in a 

 region wholly secondary, these boulders, (as they are called, 

 perhaps from the French boule, a ball,) apparently out of 

 place, have hitherto excited the attention of geologists, not 

 so much to examine and describe them, as to invent some 

 plausible theory concerning their removal from their suppo- 

 sed native seats, to their present situation. The terra incog- 

 nita of the north seems to have been generally supposed to 

 be the region from which they were removed, and the force 

 which removed them water. One conjectures, that the whole 

 of the basins of the Mississippi and of the present great lakes, 

 may, in remote times, have been one immense lake, bounded 

 on all sides, by an unbroken range of mountains, and that 

 large pieces of floating ice, from the north side, might carry 

 those blocks attached to them, and drop them, as the ice 

 melted in going south.* 



Another thinks, that " the impression is irresistible, that it 

 is the result of an immense current, or body of water, pour- 

 ing down from the north, sweeping the south side of Lake 

 Erie and all the Sciota country and Miami valley."t 



In general coincidence with these writers many others 

 might be cited, some of whom have described these boul- 

 ders, as rounded by attrition or water worn. 



I doubt much, whether such theories have ever been ad- 

 vantageous to the cause of science. So great in most men., 

 — ■ • ■ 



* Journal of Science, vol. 6, p. 98. | Journal of Science, vol. 13, p. 39. 



