A GEOLOGIST'S PARADISE BASSLER 329 



picturesque bay shore, stand as an excellent example of the cutting 

 and wearing away of the strata by wave action. Approach to the 

 cliffs south of Chesapeake Beach can be had only by the water, and 

 accordingly the student who wishes to search for fossils in the richly 

 fossiliferous Miocene strata here exposed finds a bathing suit more 

 appropriate than the characteristic hobnailed boots of the geologist. 

 In the constant wearing away of the cliffs the waves also separate 

 countless numbers of fossils from the sediments and strew them 

 along the shore, where the}^ are readily accessible to the collector. 

 These fossils range from the microscopic foraminifera, shells of 

 1-celled animals, to the enormous vertebrae of extinct whales. Fos- 

 sil sharks' teeth, some as much as 4 inches across, belonging to fish 

 living some millions of years ago, are rather common, and it is no 

 difficult task to secure a handful for stringing into a bizarre necklace. 

 Searching for these teeth by digging along the strand line and al- 

 lowing the next wave to spread out the material, thus exposing the 

 specimens, is a rare form of fishing. 



But one does not have to leave Washington to find fossilized 

 marine animals. Sea shells and sharks' teeth found in the sedi- 

 mentary sand and clay formations outcropping in the hills east of 

 the Anacostia River prove that these deposits are likewise of marine 

 origin. Good exposures of these strata, made up of Upper Creta- 

 ceous and Tertiary greensands capped by Miocene white clays 

 formed of diatomaceous earth, may still be seen at various points 

 along Good Hope Hill. The diatomaceous earth beds, composed 

 almost entirely of microscopic siliceous plant remains, are of eco- 

 nomic importance, i)articularly as a basic constituent of scouring 

 powders. Above these two formations is the Pliocene formation of 

 gravel and sand 20 to '60 feet thick containing pebbles of various 

 rocks, minerals, and fossils which afford the student many oppor- 

 tunities to add to his collection. This formation is well shown in 

 the earth mounds at Fort Totten, of Civil War fame, now overgrown 

 by vines and trees, located at the northern end of the Soldiers' Home 

 grounds. It is also to be seen in the gravel pits at Good Hope and 

 at Tenleytown. The number of minerals to be found in these gravels 

 and in the other rocks around Washington is astonishing, ranging 

 from small gold nuggets, if you are lucky, to the fool's gold or iron 

 pyrite which the earlier settlers shipped back to England by the 

 shipload. 



In the eastern part of Washington the Anacostia River, a trans- 

 verse tributary of the Potomac, parallels the fall line and cuts 

 through the oldest strata of tlie Coastal Plain where they overlap 

 the granites of the Piedmont Plateau. The student who discovers 

 the fossilized remains of land animals and plants, in the sands, red 



