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THE POPULAR SCIENCE MONTHLY 



plane, such as is represented magnified in Fig. 4, microscopically ex- 

 amined, will show that the whole substance is made up of minute, 

 many-sided cells about -^^ of an inch in diameter, and about twice 

 as long, the long way of the cells being disposed radially to the 

 trunk. The walls of the cells are extremely thin, and yet they are 

 wonderfully impervious to liquids. Looked at by reflected light, if 



Fig. 4. Cork. Horizontal Section, magnified about 300 Diameters. 



the specimen be turned, bands of silvery light alternate with bands of 

 comparative darkness, showing that the cells are built on end to end in 

 regular order. The vertical section (Fig. 5) shows a cross-section of 

 the cells looking like a minute honey-comb. In some specimens large 

 numbers of crystals are found, and are readily distinguished by the 

 aid of polarized light. Minute though they are, they are very numer- 



Fig. 5. Vertical Section. 



ous and hard, and it is partly to them that is due the extraordinary 

 rapidity with which cork blunts the cutting-instruments used in shap- 

 ing it. Cork-cutters always have beside them a sharpening-stone, on 

 which they are obliged to restore the edges of their knives after a 

 very few cuts ; and the machines we have described are for the same 



