The Mason-Wasps 



posed to wind and weather require an ex- 

 ceedingly dry stone-dust; otherwise the ma- 

 terial, already moistened with water, would 

 not properly absorb the liquid that is to give 

 it cohesion; and the edifice would soon be 

 wrecked by the rains. They possess the 

 sense of discrimination shown by the plas- 

 terer, who rejects plaster injured by the wet. 

 We shall see presently how the insects that 

 build under cover avoid this laborious 

 macadam-scraping and give the preference 

 to fresh earth already reduced to a paste by 

 its own dampness. When common hme 

 answers our purpose, we do not trouble 

 about Roman cement. Now Eumenes Ama- 

 dei requires a first-class cement, even su- 

 perior to that of the Chahcodoma of the 

 Walls, for the work, when finished, does not 

 receive the thick outer casing wherewith the 

 Mason-bee protects her cluster of cells. 

 And therefore the cupola-builder, as often 

 as she can, uses the highway as her stone-pit. 

 With the mortar, bricks are needed. 

 These are bits of gravel of an almost un- 

 varying size — that of a pepper-corn — but 

 of a shape and kind that differ greatly, ac- 

 cording to the places worked. Some are 

 sharp-cornered, with facets determined by 

 chance fractures; some are round, polished 

 6 



