172 A CENTURY OF SCIENCE 



anticlinal axes (p. 128). He also clearly recognized the 

 distinction between slaty cleavage and true dip as shown 

 in the Ordovician slates (p. 97). Between 1836 and 1840 

 he had learned a great deal on the nature of folds as is 

 shown in his Pennsylvania report for 1839 and the struc- 

 ture sections in his New Jersey report for 1840. 



R. C. Taylor, who had now become president of the 

 board of directors of the Dauphin and Susquehanna Coal 

 Company, published in the Journal in 1841 (41, 80) an 

 important paper entitled " Notice of a Model of the 

 Western portion of the Schuylkill or Southern Coal 

 Field of Pennsylvania, in illustration of an Address to 

 the Association of American Geologists, on the most 

 appropriate modes for representing Geological Phe- 

 nomena." In this paper he calls attention to the value 

 of modeling as a means of showing true relations in three 

 dimensions. He condemns the custom prevalent among 

 geologists of showing structure sections with an exag- 

 gerated vertical scale with its resultant topographic and 

 structural distortions. Taylor was widely acquainted 

 with the structure of Pennsylvania, Maryland, and Vir- 

 ginia. 



Nature of Forces Producing Folding. 



In 1825 Dr. J. H. Steele sent to Professor Silliman two 

 detailed drawings and description of an overturned fold 

 at Saratoga Lake, New York. As to the significance of 

 this feature Steele makes the following statement (9, 3, 

 1825) : 



"It is impossible to examine this locality without being 

 strongly impressed with the belief that the position which the 

 strata here assume could not have been effected in any other 

 way than by a power operating from beneath upwards and at 

 the same time possessing a progressive force ; something analo- 

 gous to what takes place in the breaking up of the ice of large 

 rivers. The continued swelling of the stream first overcomes 

 the resistance of its frozen surface and having elevated it to a 

 certain extent, it is forced into a vertical position, or thrown 

 over upon the unbroken stratum behind, by the progressive 

 power of the current." 



So far as the present writer is aware this is the first 

 recognition in geological literature of the evidence of a 



