68 



MUSHROOM CULTURE. 



that a few candles or lamps merely make it more visible. 

 The tunnel we traverse is nearly regularly arched, masonry 

 being used here and there, so as to render the support 



Fig. 22. 



Plan of large subterranean quarry at Fortes Terres, Frepillon.' S, S, S, 

 represent the plan of the bases of the huge supporting pillars, and 

 the dotted lines their union with the roof. D, C, shows the line of 

 the section shown in the following cut, and P, place for preparing 

 the plaster. Sept. 1868. 



