SCIENTIFIC SUEVEY. 925 



bution and relation of the rocks, and the exhibition of an error is 

 often as important as the discovery of a new fact. Errors in the 

 premise lead to false conclusions, therefore great care must be 

 taken to present the facts without obscurity, prejudice or igno- 

 rance. Hence, in accordance with these remarks, we will proceed 

 to point out the most important corectious that are needed in the 

 Preliminary Geological Report, 



Our later explorations go to show that a large portion of those 

 rocks called Talcose schist in the last report, belong rather to the 

 Mica schist ; for example, the great belt upon the river St. John. 

 Likewise a considerable portion of the immense Clay Slate region 

 in the central portions of the State proves to be micaceous. These 

 rocks are very obscure, and we shall say more about them further on. 



The carefully-measured regions in Machiasport, described on 

 pages 186-8, 235 and 246, have been re-published in the Proceed- 

 ings of the Portland Society of Natural History, with some addi- 

 tions, more particularly references to the catalogue of the collec- 

 tion where the specimens illustrating each stratum may be found. 



Upon page 224, line 25, 1785 should be inserted in the place of 

 1857, as the freshet there mentioned belonged to the past instead 

 of the present century. 



We find, too, that we gave unintentionally a false impression 

 respecting the character of the rocks composing the Quebec Group. 

 The inference from the language on page 227 is, that the fossils 

 near Quebec were obtained from sandstones. This is not true. 

 They were derived from limestones chiefly — as we have been privi- 

 leged to know the past season by actual inspection of the localities 

 in company with Professor T. S. Hunt, who very kindly pointed 

 them out to us. These limestones contain some of the forms of 

 life which are found in the typical sandstones further west, although 

 Mr. Billings suggests that the Quebec fauna presents some resem- 

 blance to the fauna of the calciferous sandrock. 



A re-examination of the section from Charlotte to Presque Isle, 

 fio-ured upon page 381, shows us that the amount of clay slate there 

 represented is nearly twice what it ought to be, and that none of 

 it has the south-easterly dip there represented. The error arose 

 from a too hasty examination at the first. 



Dr. Holmes informs me that he was unable to find a large bed 

 of limestone described by me as occurring near the First Seboois 

 Lake, in No. 7, R. 7, upon page 413. Nor were gentlemen familiar 



29 



