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GENERAL PLANT PATHOLOGY 



Fig. 131. — Cement cavity fillings, showing different types and successive stages. 

 I, A large cavity in an elm filled with cement blocks separated by layers of tarred 

 paper; a patented process. 2, An excavated cavity ready for treating and filling. 

 3, The cavity shown in 2, which has been nailed and partly filled with cement. The 

 ends of the rods for reinforcing the concrete are sprung into shallow holes in the wood. 

 The wire dam is sometimes allowed to remain embedded in the cement, though it 

 is usually removed as soon as the cement has partially set. 4, A later stage of the 

 work shown in 3. The height of the wire dam has been increased. 5, The same 

 cavity shown in 2, 3, and 4, several days after the filling was completed. (After 

 Collins, F. L., U. S. Yearbook Dept. Agric, 1913.) 



