THE NEWTONVILLE SAND -PLAIN. 



i. Introduction. — During the past year the writer has studied 

 the Newtonville (Massachusetts) sand-plain under Professor 

 Davis, of Harvard University, and after studying the deposit as it 

 now exists, made a detailed map of the plain with its feeding esker. 

 Then a model of the region was made in clay on the scale of 

 1 : 4000. This clay model was photographed, and is here repro- 

 duced in half-tone, in Fig. 1, Newtonville Sand-plain. The con- 

 ditions of formation were then studied, and a second model con- 

 structed, showing a conjectural relation of deposits to the margin 

 of the New England ice-sheet at the time of its formation. A 

 photographic reproduction of this is given in Fig. 2, Ice-sheet 

 Restored. 1 



2. Making the models. — The clay was built up in a solid mass 

 to the greatest required height, and the details of form were then 

 cut with graving tools. In making such models it is essential 

 that the foundation for the clay should be firm and not liable to 

 warp. A slate slab, or a piece of heavy plate glass answers 

 the purpose well. While at work on the model it is important 

 to keep the clay moist. So a box lined with rubber cloth should 

 be provided, large enough to cover the clay without touching it, 

 and an inner layer of muslin put in to hold the water. When the 

 model is ready to have a plaster mold made, the edges should be 

 trimmed square, tapering slightly up from the slate so that the 

 mold will slip off easily, the surface oiled, boards placed an inch 

 and a half from the four sides, and liquid plaster poured over it. 

 After the plaster has set, it may be wedged up from the slate or 

 glass, and lifted from the clay. Then the plaster negative should 

 be carefully washed with a brush to remove all oil or clay stick- 



1 Teachers or others who desire copies of models, photographs, or lantern slides 

 can arrange for them by corresponding with the writer. 



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