189S] JAMES HALL 263 



That office and the similar position for the state of Wisconsin, 

 which Hall received in 1857, he was able to hold without affecting 

 his position in the New Fork service. His work in connection with 

 these surveys increased his knowledge of the geology of the Missis- 

 sippi basin; and he was able to make important additions to the 

 geology of the western states, as he was entrusted by the Federal 

 Government with the description of the collections made by 

 many of the expeditions and surveys in that region. Tims he 

 described the fossils collected by the Fremont expedition, the 

 collections of the Pacific Railway Survey, the Cretaceous fossils 

 obtained by the Mexican Boundary Commission, and wrote a 

 report on the geology and palaeontology of the basin of the Great 

 Salt Lake of Utah from materials brought back by Lieutenant 

 Stansbury. 



In 185 6 Hall was elected President of the American Association 

 for the Advancement of Science. At its meeting in Montreal in the 

 following year he gave his famous address, in which was first 

 definitely expounded the theory that the elevation of mountain chains 

 is due to the deposition of sedimentary deposits, and that the direction 

 of the mountain chains are determined by lines along which the 

 thickest accumulation has taken place. 



But this and similar incursions into the domain of physical 

 geology only temporarily distracted Hall from palaeontographical 

 work to which his inexhaustible energies were mainly devoted. 

 His additions to the materials of invertebrate palaeontology are 

 probably greater than those of any other man. The number of 

 important new genera founded by Hall is enormous. The roll of 

 Hall's new genera and species was by 1858 so long, that Colonel 

 Portloek, the President of the Geological Society whose duty it was 

 to present Hall with the Wollaston Medal, felt bound to qualify his 

 patronizing commendations by a warning that he was himself ' : prone 

 to hesitate respecting new species when closely allied to previously 

 known species." But the work which Colonel Portloek appeared to 

 disparage is now recognised as Hall's most permanent title to fame. 

 As a note in the Geological Magazine reminds us, palaeontology is 

 indebted to Hall for the following important genera : among the 

 graptolites there are Gallograptics, Dicranograptvs and Phyllograptus ; 

 among the corals, Coelophyllum, Heliophyllum and Streptelasma; 

 among the Pelmatozoa, Calceocrinus, Heterocrihus, Dendrocrinics, 

 Glyptaster, Glyptocriniis and Hemicystis; there is the star-fish 

 Palaeaster, and the echinid Lepidechinus ; the additions to tin; 

 Monticuliporoids and Bryozoa are very numerous, including Favistella, 

 Gallopora, Bactropora, and Tvematopora ; and among the Trilobites 

 aie Pleuronotus, Bathynotus, Mesothyra and Ptyehaspis. His Memoir 

 on North American Eurypterida, Pterygoti and Geratiocans (1871), 



