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PREFACE. V 



1 may be accused of fickleness on account of the chang- 

 es which appear hi every successive book I pubhsh. I con- 

 fess this is the ninth time I have published a geological no- 

 menclature ; and that I made changes in each of more or 

 less importance. But I have always consulted my scientific 

 friends ; and every change was founded on new discoveries 

 in "matters of fact." In this text-book, the principal 

 changes relate to the graywackes. The Allegany moun- 

 tains, 1 had never examined before with particular care. I 

 verily think, these mountains present every thing required 

 for settling that part of the science. The various deposites 

 of Detritus had not been thoroughly studied by any 

 American, when I published my last nomenclature. I 

 believe I have made a few changes in that department, 

 which will finally obtain. I now adopt the Tertiary 

 formation of Europeans ; but I find no facts here to justi- 

 fy their numerous subdivisions. 



I can now give European equivalents for all our strata, 

 excepting the ferriferous and geodiferous. Our fourth series, 

 however, seems to be more solid, harsh, and vastly more 

 extensive, than its supposed equivalent. Perhaps it is a re- 

 petition of our third series. It is certainly distinct in the 

 range of the profile given at the foot of the map, however. 



With all deflerence to the high character of La Bache ; 

 as an experienced teacher I may say, that his numerous sub- 

 divisions, if adopted, will ruin the science.* Others have 

 done much towards driving the study from our schools, by 

 introducing petty local names. If their authors were not 

 entitled to high respect, on account of other services to the 

 science, one would feel disposed to treat such names ludi- 

 crously. For example, there is a variety of first graywacke 

 in a place called Pilfershire, in Columbia county, remark- 



» See Table of Equivalents at the end of this Text-Book. 



