112 B. WILLIS—DRIFT PHENOMENA OF PUGET SOUND. 
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Generalistatememtrc sine eae e che care peneys cere rs, caste Stee eres ae 141 
The Washonfelaciall epochs. n2icveciaecrseerae ene abe aise. ons oistareee re eee . 141 
Definition of terms.............. Faint Cerne eI RC A Cie a Gil GA-d'S 0 141 
Summany of they Vashonvhistomyare eect leek eee eee 141 
CORSO alee en a Sar ayer ARONA COME e omlbs Msn snd 6 Os 66.00% 148 
Osceola clays...... ra een Se ene as oO EME OMNES GS co.0 3c 144 
Doutiy. eravelsiir oi csessvansin choker toca eneteue Ges ee he ea Pa) eee TR ee 144 
Puyallup interglacial epoch.................. PO Seed dones Ae 145 
iistony of therAdminalivece-shee immer errr en areeee nee 145 
Ruyallupisand sSieeee eases eee eee eee eens rok bcaite eet neltsrsieaeteas Tee TOS . 146 
Orting eraviel Stary terys vist eee ercieer cic see ecm atonal a\s uses toto eR eer ered 147 
Evidences of mild climate........... Seite eae each: olay os 148 
Macomiaydeltaey ae veetiet kev eae es hos eee eee Lor aati eee 151 
Admiralty glacialyepochecei tates classe ce srt nomen ei eee 152 
General statement ay ie aoe oun seta anf eae aie eps ae ee Oe 152 
Admiralty billjandeclaysancmerias ceca ae cic tence eee ae eee 152 
SMM AEs MmOG ade be pcedssonudnodoooGhdooEsocmoErodudopatoocoDDsGoDONSoOO 153 
Tabulated' sections». so ehas stem nein ation theese nA Et aioe ee 157 
INTRODUCTION 
In the following paper I propose to present some facts of topography 
and of Pleistocene geology bearing upon the origin of the peculiar phys- 
iography of the Puget Sound basin. ‘The observations were made dur- 
ing the summer of 1896 in the southeastern portion of the Sound basin, 
in the course of a careful survey of the Tacoma quadrangle and the adja- 
cent districts. I was assisted by Mr George Otis Smith, of the United 
States Geological Survey, and was so fortunate as to be associated during 
the inception of the work with Professor I. C. Russell, who had spent the 
three weeks preceding in a reconnoissance of the shores of Admiralty 
inlet. The observations would have been far less complete and their 
interpretation less definite but for the aid and helpful discussion given 
me by these geologists. 
GENERAL RELATIONS 
ADJACENT MOUNTAIN RANGES 
The Cascade range and the Olympic range are mountain masses of Mio- 
cene and earlier sediments, with granitic intrusions of undetermined age, 
upon which volcanic flows and cones have accumulated. The former 
range lies to the east, the latter to the west, of the Puget Sound basin. 
Their general altitude is from 6,000 to 7,000 feet (1,800 to 2,100 meters) 
above sea. Passes are cut down to 3,000 feet (910 meters), and isolated 
volcanoes rise far above the more numerous peaks of plutonic and sed- 
