MINERS "CHOKE-DAMP. 129 



height of about eighteen feet from the ground. 

 The only plant which flourishes there is the 

 tall and fearfully-poisonous Pohon Upas-tree, 

 which grows luxuriantly amid a scene of the 

 gloomiest description. This gas is in other' 

 districts so abundantly evolved from the earth 

 as to be heard issuing with a hissing noise 

 from cracks in the limestone ; and it often proves 

 fatal to birds which unconsciously come within 

 its influence. 



Carbonic acid appears, however, under circum- 

 stances where volcanic agency plays no part. 

 Effusions of this gas take place in the vicinity 

 of extensive layers of wood-coal, principally, 

 however, in the form of an aqueous solution ; 

 in other words, as carbonated springs. The 

 gas may often be seen bubbling around the 

 edges ; and the pleasant waters of some of these 

 springs make them a valuable possession to the 

 inhabitants. 



From these considerations we learn, that the 

 effusion of this gas is an indication of two classes 

 of chemical activities first, of volcanic decom- 

 positions ; and, secondly, of those more gradual 

 changes which time produces in the constituents 

 of the coal-layers or measures. Both these 



nature of the trees, it must not, therefore, be supposed that 

 the whole matter is fabulous. The statement above given 

 has been abimdantly confirmed by modern travellers. 



K 



