millkkJ IVORK OF GLACIERS 123 



0. Buds and twigs more slender, both l)uds and twigs (at least to- 

 ward tip ) white-downy, white lines al)sent from bark. Mountain Maple 

 {Acer spicatiim). 



6. Buds brown, narrow, sharp-pointed, generally -l-S pairs of close- 

 ly over-lapping scales visible, collateral buds absent, Sugar Maple (Acer 

 sacclwntni ). 



0. Buds red or green, broader, blunt-pointed, fewer scales visible, 7. 



7. Terminal buds small, red, generally under ."j mm. long and not 

 distinctly larger than lateral buds ; collateral buds generally present ; pith 

 often pink; native trees. 8. 



7. Terminal buds large, stout, generally over 5 mm. long and gener- 

 ally distinctly larger than lateral buds ; collateral buds never present ; 

 European trees, 9. 



8. Broken tvvigs with rank odor, bark falling away in large, thin 

 flakes on old trees, branchlets strongly tending to grow downward and 

 curve upward at their tips. Silver Maple (Acer saccharimiiii) . 



8. Broken twigs without rank odor, bark rough on old trees but 

 generally not flaking in large thin scales, l:)ranchlets less markedly curved, 

 Red Maple (Acer rnbrniu). 



'J. lUids red, inner scales covered with rusty wool; adjacent edges of 

 leaf-scars meeting and forming a slight projection: l)ark close-ridged. 

 not flaky, Norway Maple (Acer platatwides). 



9. Buds green, inner scales white-woolly, edges of leaf-scars not 

 meeting, bark flaking off in squarish scales. Sycamore Maple (Acer 

 Pseiido-PIafainis) . 



Work of Glaciers 



Geo J. ]\riLLr-;R. 



This article has been arbitrarily limited to a discussion of the 

 more common glacial features to be found within the area cov- 

 ered by ice during the Glacial Period. Since few of the evidences 

 of glaciation can be brought into the school-room the tield is the 

 only place to gain any true concept of the work of glaciers. On 

 the other hand the large area of some of the common glacial fea- 

 tures necessitates considerable traveling in order that the student 

 may see enough to comprehend them. Xothing but continued 

 field experience can give familiarity with glaciation. For con- 

 venience and to secure definiteness the subject is discussed under 

 two headings, viz.. Work of Erosion and \\'ork of Deposition. 



WOKlv OF EROSION. 



Let us assume that the class enters a glaciated valley at its 

 lower end and ascends to its head. What is the first large feature 

 to be noted? If a good view point can be secured the characteris- 

 tic U-shape (Fig. 1) will be observed. This should be contrasted 

 with the \'-shape given to a valley b}- running water. Is this 

 U-shape sufficient proof that a glacier ever occupied the valley? 



