382 iiKsozou; il()i;a.-> uf umikd >tates. 



and pass below the base of the section, havintr a tliickness of about 20 

 feet. They contain clay lenses and nodules, i)ut, as on the -Tames River, 

 the Ijasal clays have disappeared. An excellcMit view of this exposure 

 was taken while it was fresh. This is shown in PI. LXXIV. 



Views were also taken of the fine exposure* on Kansas avenue near 

 this same place and between the Adams Mill I'oad and Ontario avenue. 

 One of these is shown on PI. LXX\\ It wa.s in these sands on this street 

 that a fine silicified trunk was collected by ^Ir. Karl Woodward (son of 

 Prof. R. S. Woodward), and presented to the Xational :\Iuseum, where 

 it bears the museum Xo. 8603. It doubtless belongs to the genus Cupres- 

 sinoxylon (Sequoia), to which Doctor Knowlton referred all the trunks 

 examined by him, several of which were found in the city of Washington. 



Views were also taken of the fine exposures on the east side of Six- 

 teenth street through ^leridian Hill. The contact with the crystalline 

 rocks was not reached in the excavations here made, but the Potomac 

 beds were w^ell exposed. The cross-bedded white sands are beautifully 

 shown, but these are overlain l)y more argillaceous, irregulai-ly stratified 

 beds that foi'm the lowest part of the exposures near the top of the hill, 

 the cross-bedded sands running under them on the southern slope. Four 

 views were taken, but two of these are so nearly duplicates of the other 

 two that they add little to them. The view shown in PL LXXVI w^as 

 taken from the south side of Crescent street looking northeast, and is 

 therefore panoramic or diagonal to the exposure. The view may be 

 better understood ]j>- reference to the section (section 10) on page 386, of 

 these same beds. It covers about 10 feet, beginning very close to the 

 Columbia cap and a little l)elow the point where the sands disappear 

 beneath the roadl)ed, and ending some distance south of the point where 

 the Potomac clays do the same. The few specimens of poorly pre- 

 served fossil plants were found in the freshly plowed roadbed opposite 

 these exposures (see p. 385). 



This work was resumed early in the spring of 1893, and on April 16, 

 accompanied l)y Messrs-. Victor Mason and William F. Willoughby, I dis- 

 covered an important plant bed near Fairfax Seminary, in a gulch known 

 as Chinkapin Hollow. It is a short distance south of the Leesburg pike, 2 

 miles northwest of Alexandria and 1 i miles northeast of Fairfax Seminary. 



