ILLUSTRATIONS. 
Page. 
Plate I. Outline map of Seward Peninsula, showing position of York region, 
Alaska ■. 8 
II. Topographic map of York region : 12 
III. Valley of Lost River from the coast 20 
IV. Cape Mountain 22 
V. A and B, Thin sections of altered porphyritic dike near Tin Creek. . 24 
VI. A and B, Thin sections of porphyritic dike on Ear Mountain 26 
VII. A, Thin section of luxulianite from Ear Mountain; B, Polished sur- 
face of tin ore from Lost River 28 
Fig. 1. Sketch of the coast from Cape York to Cape Prince of Wales 9 
2. Geologic sketch map of York region 13 
3. Sketch map of Lost River 18 
4. Sluice boxes used in washing placer tin in York region 33 
5. Box used in washing stream-tin concentrates 34 
5 
