496 REPORT OF NATIONAL MUSEUM, 1904. 



As previously noted (p. 433), J. G. Norwood. State geologist of Illi- 

 nois, was succeeded in 1858 by Amos H. Worthen. Under the hitter's 

 direction the survey lasted until 1875, when active Held work was dis- 

 continued, owing" apparently to an indisposition on 



AmosH. Worthen's ' ° f \ * • , , 



Work in Illinois, the part of the legislature to provide the necessary 



1 858-1 875 



funds. Six volumes of reports had been issued up to 

 this time, and by the aid of subsequent special appropriations, two 

 more were completed, the last bearing the date 1890, and on the title 

 page the name of Joshua Lindahl, State geologist, and Worthen as 

 director. The total published resujts of this survey amounted to 

 upward of 1,000 pages of text and 197 full-page plates of fossils. 



Worthen was aided at various times during the work by J. D. 

 Whitney, Leo Lesquereux, Henry Engelmann, J. S. Newberry. F. B. 

 Meek, II. C. Freeman, II. M. Bannister, II. A. Green, James Shaw, 

 G. C. Broadhead, Orestes St. John, and E. T. Cox. The work of 

 Whitney naturally related to the mining problems of the State, 

 Lesquereux to the paleobotany. Meek to the invertebrate paleontol- 

 ogy, Newberry to the vertebrate paleontology, and the others men- 

 tioned to general stratigraphy. 



In the first volume of his work Worthen divided the sub-Carbon- 

 iferous into five groups: The Chester, St. Louis, Keokuk, Burlington, 

 and Kinderhook, the term Chester group being used in place of the 

 Kaskaskia of Hall, and the St. Louis including the Warsaw of Hall. 

 The blue, green, and chocolate-colored shales immediately underlying 

 the Kinderhook group in western and southern Illinois he regarded as 

 Devonian. 



Whitney, in his report, regarded the Galena limestone as the "sole 

 depository of lead in western Illinois/ 1 a view not quite in agreement 

 with that expressed with reference to the Iowa and Wisconsin fields. 

 Two maps were given in this report — one a geological map of the 

 northwest corner of the State, and the other showing a diagram of 

 the lead-bearing crevices near Galena. The origin of these lead- 

 bearing crevices "seems to be the same cause by which what are called 

 joints by geologists have been formed in almost every variety of rock, 

 occurring in large homogeneous masses, and especially where a decided 

 crystalline texture exists in them." The course of the main set of 

 fissures he thought might have been determined by the axis of 

 upheaval, by which the whole region had been slowly elevated along 

 the north boundary of the district, the metals themselves having been 

 held in solution in oceanic waters and precipitated through the agency 

 of decomposing organic matter/' 



"This is essentially the view held to-day, with this difference: Most geologists 

 believe that the ore was originally disseminated throughout the limestone, and that 

 it has become segregated in veins and pockets through the leaching action of 

 meteoric waters. 



