100 
GEOLOGY 
1 give here a fac simile of the map — Plate IX — and the author’s memoir, as the starting 
point for the history of the progress of American geology. 
(Extract from Transactions of the American Philosophical Society , held at Philadelphia , for promoting useful knowledge, 
Yol. VI , page 411 etc. ) 
Observations on the Geology of the United States, explanatory of a Geological Map. 
~ see plate IX ") — by William Maclure. 
Read January 20th , 1809. 
Necessity dictates the adoption of some system, so far as respects the classification and arrange- 
ment of names the Wernerian appears to be the most suitable, First, Because it is the most perfect and 
extensive in its general outlines, and secondly, The nature and relative situation of the minerals in the 
United States, whilst they are certainly the most extensive of any field yet examined, may perhaps be 
found to be the most correct elucidation of the general exactitude of that theory, as respects the rela- 
tive position of the different series of rooks. 
Without entering into any investigation of the origin or first formation of the various substances, 
the following nomenclature will be used. 
Class 1st. Primitive Rocks. 
1. 
Granite , 
8. 
Porphyry , 
2. 
Gneiss, 
9. 
Sienite , 
3. 
Mica slate. 
10. 
Topaz-Rock , 
4. 
Clay slate. 
11. 
Quartz-Rock, 
5. 
Primitive Limestone, 
12. 
Primitive Flinty-Slate , 
6. 
Primitive Trap, 
13. 
Primitive Gypsum, 
7. 
Serpentine , 
14. 
White-Stone. 
") Want of color indicates that the common boundary is not ascertained, the two classes of rocks being some- 
what intermingled ; or that such portions of the United States have not been examined. 
« embraced his accumulated facts, w'as at length submitted to the American Philosophical Society, and 
((printed in their Transactions for the year 1809 ». (See: A Memoir of William Maclure, Esq.; by Dr. 
Samuel George Morton, page 11; Philadelphia, 1841.) 
Maclure continued to extend and complete his geological survey , and in 1817, he published: ((Ob- 
servations on the Geology of the United States of Eorth America; with remarks on the probable effect that may 
be produced by the decomposition of the different classes of rocks on the nature and fertility of soils; applied 
to the different States of the Union, agreeably to the accompanying Geological Map. With two Copper- Plates. 
— Read May 16’'' 1817 ». (In the Transactions of the American Philosophical Society, vol. I, new' series; 
Philadelphia, 1818.) This was only a revised edition of his first work published in 1809. He was one 
of the first members and early chosen President of the Academy of Natural Sciences of Philadelphia, 
and was one of the most active and liberal supporters of the social scheme established by Robert Owen 
at New Harmony. To this w'estern wilderness, in a country where society consisted of backwoodsmen 
and trappers, Maclure transported in 1824 the most splendid library on Natural History then existing 
in North America, and gathered round him a distinguished circle of naturalists, among whom were Tho- 
mas Say, C. A. Lesueur, C. S. Rafinesque, Dr. Gerard Troost, Robert Owen himself and his interest- 
ing family. The celebrated David Dale Owen , the true successor of Maclure in the geology of the Mis- 
sissippi valley, was then a boy, and has probably derived his love and knowledge of geology from his 
early association with this celebrated company of savants. The later years of Maclure’s life were passed 
in Mexico, where he died, at San Angel, the 23'' day of March 1840, in the seventieth year of his age. 
