36 



edge of the opening to the deepest point of the nest trough ; and those 

 of the fourth the thickness of the bottom. 



The following are the measurements in millimetres of the diameters 



A 1 . 



so 



27 



ISO 



292 



B. 



230 



c. 



GO 



300 



70 



490 



D. 



275 



70 



490 



mm. 



Total Heights 

 of the Nesting- 

 boxes in milli- 

 metres. 



of the inside of the nesting-cavities at the various points as indicated 



in the above diagram : 



; 

 Nesting-Boxes 



B. C. D. 



80-85 

 85-95 



Size A. Al. 



At A. 60-65 60-65 



B. 70-80 70-80 



C. 85-95 85-95 115-125 160-180 160-180 

 These boxes are made of alder, birch, pine, and other woods which 

 do not split easily.* 



* Many boxes were made of birchwood. Baron von Berlepsch has forbidden 

 the use of this wood in future as it is not very durable. 



