274 GEOLOGICAL EXCURSION TO THE KOCKY MOUNTAINS. 



WASHINGTON, D. C, TO CUMBERLAND. MO. 

 [TINERARY. 



By <;. II. Williams. 



Distanoe. Elevation. 



Station. 



a 



Washington * 



Terra Cotta 4 



Silver Spring 7 



Garretl Pari 12 



Koekvillo I 16 



Derwood 19 



Gaithersburg L ,- J 



Boyd 30 



Diokeraon 86 



Tuacarora 39 





Distance. 



siat ion. 



10 



I! Washington .Function 



(> Point of Books 



li Weverton 



19 Harpers Ferry . 





43 



4:t 

 52 

 55 



26 Martinsbnrg 74 



3] North Mountain 81 



3."> Cherry Run 87 



48 Hancock 96 



58 Cumberland t L52 



68 i 



69 

 69 

 84 

 89 

 119 

 [80 

 140 



ir>4 

 245 



Kiev at tun 



229 



E 

 S 



70 



'J 10 

 'J72 

 c.;i4 

 .M7 

 398 

 474 

 689 



70 

 83 

 193 

 107 



12] 

 148 

 195 



• Population, 280,392. 



i Population, 12,729. 



Washington. On leaving Washington, the railway line at ftrsl passes 

 over the unconsolidated deposits of the Coastal plain. The lowest of 

 these is the Potomac series (of early Cretaceous or late Jurassic age), 

 consisting- of coarse littoral conglomerates at the base, formed of well- 

 rounded pebbles of qaartzite. Above the conglomerates are a series 

 of variegated clays, often valuable for pottery, and sometimes contain- 

 ing deposits of limonite. 



Terra Cotta. At this station are works where drain pipes, etc., are 

 made from the clays of the Potomac series. 



Silver Springs, on the northern boundary of the District of Colum- 

 bia. The rock here is a very granitoid, though much rotted, gneiss. 

 It is not visible from the cars. The road then passes over typical nolo- 

 crystalline gneiss, with steep westerly dips, to 



Garrett Park, where, these are cut by serpentine and a still later 

 hornblende granite, tilled with included fragments of the surrounding 

 gneiss. 



Rockville, a thriving town, recently much developed as a suburban 

 residence part of Washington. The division between the crystalline 

 and semicrystalline portions of the Piedmont plateau passes just west 



