Manchester Memoirs, Vol. xlvii. (1903), No. 4- 9 



earth becomes too fatiguing on account of the length of 

 the tunnel, the mole will often begin to make new tunnels 

 from runs close to the edge of the fortress {Fi^s. 5, 6). 

 Sometimes these new runs break into those leading from 

 the nest-cavity, but not very often ; usually they lie above 

 them.* 



The tunnels in the fortress are for two distinct 

 purposes : — 



(a) Tunnels to eject earth from the nest-cavity and 

 bolt-run. These are generally in the shape of a corkscrew 

 ascending from the nest, and often diverging into blind 

 terminals (/^z^. 10). 



T'i'jf. 10. — Vertical plan ol fortress shown in Fi^. 4, showing spiral gallery 

 and blind terminals. 

 /', c, af. — Outlets. 



^,y;— Two bolt-runs. 



{b) Tunnels not connected directly with the nest- 

 cavity, but traversing the fortress from runs outside it. 

 Through these tunnels the mole has brought earth to 

 heap over the nest, and they seldom occur except in boggy 

 land, where the nest is of necessity near the surface of 



* In sandy soil, if the weather is dry, all the tunnels fall in as soon as 

 formed, and the mole pushes the material right through the loose heap, but 

 if the weather is damp, the superincumbent sand hardens, and the tunnels 

 remain. The same thing happens in peaty soil. 



