8 



♦ KNO^ATLEDGE ♦ 



[November 1, 1887. 



exert tbat amount of pressure against any unyielding 



resistance. , , <- • i 



From this it will be understood bo«' a g.ile of wind may 

 be made to blow along the dark subterranean roads of a 



deep coal-pit. I may add that the figures above rather 

 under-estimate the actual force, as I have taken the air at 

 surface density. It actually increases as we descend— 

 increasing, of course, all the quantities named. 



THE ONE-SCALE ATLAS. 



Map IX. 



by-Ric3i4 A.Proctor . 



Tli* loi£ar seal* nudiaJly is itra/brnv 



^naUr by ij!5*^ hulfymy to «A* •d^'*' 

 anA. &yfJ*V^ at thx, eAge . 



e H IDS iM wo "oo BOO 'O"* 



MAP 12 



SmnJl areas art. qrt^itxr hy y6S*^haJf 

 ^mytothe>edg»,a.id.hyyUt^ai. ths^ 



EcMWaliea-.Za^ 



