382 MESOZOIC FLORAS OF UMTED STATES. 



and pass below the base of the section, having a thickness of al:)Out 20 

 feet. They contain cla}^ lenses and nodules, but, as on the James River, 

 the basal clays have disappeared. An excellent view of this exposure 

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



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

 this same place and between the Adams Mill road and Ontario avenue. 

 One of these is shown on PL LXXV. It was in these sands on this street 

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

 Prof. R. S. Woodward), and presented to the National Museum, where 

 it bears the museum No. 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 Meridian Hill. The contact with the crystalline 

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

 beds were well exposed. The cross-bedded white sands are beautifully 

 shown, but these are overlain by more argillaceous, irregularly stratified 

 beds that form 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 was 

 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 by 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 below the point where the sands disappear 

 beneath the roadbed, 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 by 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 Ih miles northeast of Fairfax Seminary. 



