C. D. 4 Walcott — The Taconic System of Emmons. 307 



The second type is like warringtonite from Cornwall, de- 

 scribed by Maskelyne.* This variety was suspected by Mr. 

 Pearce (loc. cit., p. 135). It is of a light green color and has a 

 curved doubLe wedge-shaped habit. The forms observed are 

 shown in figs. 7 and 8. The crystals were poor for meas- 

 uring, all the plaries, with the exception of b, being curved to a 

 great degree. The crystals were none of them more than 2 or 

 gmm long^ w ith the relative proportions of the figures. They 

 were implanted by fry m, in fig. 7, was identified with. cer- 

 tainty, the angle for h^m being 52 Q approximately. The 

 plane lettered h was very much curved in all cases and its sym- 

 bol, consequently, is not known with exactness. It corresponds 

 in its angles very roughly, it is true, to the k, 12. 1 .4, of 

 Schrauf ; some of the angles obtained from these crystals and 

 the corresponding ones of Schranf's warringtonite being given 

 here : 



Washington. Schrauf. 



b ., ft, 010,-. 12. 1.4 .= 80°-82° 86° 43' 



m~k, 110^12.1.4 _= 45° 43° 11' 



ft ^ ft', 12. 1,4: 12.1.4= 75°-80° 



In most of the crystals of this type h was undulating parallel 



to c. 



Want of material forbade an analysis of this mineral, but 

 blowpipe tests and the crystallographic examination establish 

 its identity beyond doubt. 



Aet. XXY I.-f-jTAe Taconic System of Emmons^nd the use of 

 the name Taconic in Geologic nomenclature^ by Chas. D. 

 Walcott, of the U. S. Geological Survey, y ith Plate III. 



(Continued from page 242.) 

 Geology of the Taconic Area as known to Dr. Emmons. 



(1). The strata referred to the " Taconic System ;" (2). The 

 stratigraphic position of the " Taconic System." 



Dr. Emmons began the study of the Taconic area in Berk- 

 shire County, Mass., and from there extended his investiga- 

 tions, to the north, into Bennington County, Yt., and to the west, 

 into Washington and Rensselaer counties, JST.-T.f In 1842,^: 



* Ch. News, x, 263, 1864. Phil. Mag., IV, xxix, 475. 



f " My first business is to sketch a picture of the oldest of the sediments, as 

 they are exhibited in a series which collectively constitute the Taconic System 

 and as it is developed in the Taconic ranges of Berkshire and the adjacent 

 country immediatelv north and south." (Am. Geol., pt. 2, p. 5, 1856). 



\ Geol. N. T., pt 2, p. 144, 1842. 



