No. 7.] G. M. DAWSON — SURFACE GEOLOGY. 395 



with a second about 30 feet higher. la following the Cowlitz, 



banks in cuttings sometimes 50 feet in height, show fine, yellow- 

 ish horizontally-bedded sands. These are pretty hard, and are 

 interbedded in places with thin and thick layers of gravel, com- 

 posed of water-rolled stones, some as large as the two fists. The 

 sandy drift exactly resembles that seen in low banks near the 

 water level on the Willamette and Columbia, but as we go north- 

 ward, and ascend, the gravelly layers continue to increase in im- 

 portance. Forty miles from the Columbia the railway passes 

 over a distinct and wide bench with an elevation of 337 feet, the 

 general level of the country — which is here nearly flat — being 

 about 380 feet. Gravel beds are abundant at Centreville (54 m.) 

 with a general elevation of about 160 feet. Here the rolled 

 gravel of the subsoil contains some small boulders up to tea 

 inches in diameter. At 65 miles from our initial point, eleva- 

 tion 230 feet, boulders two feet in diameter are first seen, and 

 a few miles further northward gravelly banks are found, of 

 rudely mingled coarse materials, including boulders up to three 

 and four feet in diameter, with overlying or interstratified layers 

 of fine yellowish sand. The country here becomes undulating, 

 with many low ridges and hillocks, and begins to show small 

 ponds and swamps. A few miles south of Yelm Prairie (74 m., 

 elevation 295 feet), some ridges, in their composition resemble 

 the closely-packed gravel and boulder deposits of Spring Ridge 

 and Beacon Hill near Victoria. From this point to Tacoma, 

 the county is generally flat or gently undulating, and declines 

 gradually toward the head of the Sound, the superficial deposits 

 being in general not so coarse as those just described. 



At Tacoma, the banks along the shore show a great thickness 

 of firm finely-bedded sandy and clayey deposits, which form the 

 substratum of the plateau above, but which I had not time to 

 examine. At Seattle — the centre of the coal mining industry — 

 about 30 miles northward on the east shore of the Sound, the 

 drift consists of sands, gravels and clays, without any apparent 

 regular sequence, but with occasional large and many small 

 boulders scattered through them. The sands are frequently 

 current-bedded, and in one place curiously contorted layers of 

 fine, hard, clayey sand, alternated with others nearly horizontal, 

 as though floating ice had from time to time disturbed the regu- 

 larity of the deposit. Some beds resemble in all respects true 

 boulder-clays, being thickly packed with large and small stones, 

 Vol Till. z No. 7. 



