4 The America/n Geologist. Jan. i89i 
to his friend Dr. Charles T. Jackson, of Boston, to know if he 
could recommend a young mineralogist for the position. Jack- 
son designated the son of a miller of the village of Hingham, 
near Boston, named James Hall, who used to come often to his 
office, bringing with him minerals to determine and borrowing 
books. Acting on the recommendation of Dr. Jackson, Dr. Em- 
mons appointed James Hall for his assistant, and during the first 
season of the survey Mr. Hall gave much of his attention to the 
ores of iron in the northern district of New York. 
During the second season of exploration, Dr. Emmons named, 
described, and classified the Potsdam sandstone, so celebrated 
since. The first time that the <■ Sandstone of Potsdam " is used 
in geology is at p. 214 of the second annual report of the "2nd 
Geological District" of the state of New York, by Emmons, 
1838. Notwithstanding the excellent description given by Dr. 
Emmons, never has a well defined group of strata been so little un- 
derstood and so erroneously made use of. Beds ranging from the 
Pamdoxides argillites of Braintree inclusive to the Triassic sand- 
stone of lake Superior, have been referred to it, at random, with- 
out the smallest appearance of identity or even of close affinity l 
In 1838 Dr. Emmons began to make observations which led 
him in 1842 to create below the Potsdam sandstone the great 
Taconic system, composed of a series of strata twenty-five to 
thirty thousand feet thick. At first he did not find fossils, but 
two years later he published his memoir on ' ' the Taconic s\-s- 
tem " with fossils unknown in any other S3'stem and as he says, 
" peculiar to the black and the Taconic slates." The discovery 
of Taconic fossils was made in September, 1844, near Bald moun- 
tain, in the state of New York, and they were published in Decem- 
ber of the same year at Albany, under the names of Atops trilin- 
tutus, Elliptocephala asaphoides, Nemapodia tenuissima, and 
Fucoides (graptolites) simplex. It was the first discovery and de- 
scription of the Primordial fauna, all the world over ; a discovery 
proved by dates and advocated by Barrande. the first authorit}* on 
the Lower Palaeozoic palaeontology. (-'On the use of the name Ta- 
1 The identification of rucks to the Potsdam sandstone of Emmons, 
constitutes a singular chapter in the history of the progress of Ameri- 
can geology. Even to this day. we have the curious spectacle of a 
Head of Division of the U. S. Geological Survey who contrives to refer 
to the Potsdam, any strata of the Taconic system, whenever wanted at 
any special and convenient place to suit the purely imaginative and 
ever changing classification of his so-called American Cambrian. 
