1636 THE STORY OF THE UNIVERSE 



the departure of the Anthophora to endeavor to pene- 

 trate into their nests and lay their eggs there. The 

 gallery of entry and exit has been built with grains 

 of sand, the debris produced by the insect in work- 

 ing. These grains of sand glued together form, on 

 drying, a very resistant wall. 



The other animals of which I have to speak are 

 genuine masons, who prepare their mortar by tem- 

 pering moistened earth. Every one has seen the swal- 

 low in spring working at its nest in the corner of a 

 window. It usually establishes its dwelling in an 

 angle, so that the three existing walls can be utilized, 

 and to have an inclosed space there is need only to 

 add the face. It usually gives to this the form of a 

 quarter of a sphere, and begins it by applying earth 

 more or less mixed with chopped hay against the 

 walls which are to support the edifice. At the sum- 

 mit of the construction a hole is left for entry and 

 exit. During the whole of its sojourn in our country 

 the swallow uses this dwelling, and even returns to 

 it for many years in succession, as long as its work 

 will support the attacks of time. The faithful return 

 of these birds to their old nest has been many times 

 proved by attaching ribbons to their claws; they have 

 always returned with the distinctive mark. 



Besides the swallows, birds offer us several types of 

 skilful construction with tempered earth. 



The flamingo, which lives in marshes, can not 

 place its eggs on the earth nor in the trunks of trees, 

 which are often absent from its domain. It builds a 

 cone of mud, which dries and becomes very resistant, 

 and it prepares at the summit an excavation open to 



