76 gas-jets; mud- volcanoes. 



constant jet, as from the bored spring-well at 

 Nauheim, or in an intermitting stream, as 

 at Kissingen, or in a jet continuous but varying 

 in height, as from the "Sprudel" of Carlsbad, 



Carbonic acid issues from the earth in number- 

 less places, even without its usual accompaniment 

 of water. Such jets or springs of gas are called 

 Mofetti. Wherever they come up, they are de- 

 structive of the life of plants. Spots therefore, in 

 which carbonic acid is thrown off in large quan- 

 tities, are always marked by being devoid of 

 verdure. They are met with especially in places 

 where volcanoes are still at work, or where there 

 are still traces of ancient volcanic agency : for 

 instance in the Eifel, in the Weser hills, in the 

 Wetterau, in the neighbourhood of the Bohemian 

 baths, in Auvergne, &c. 



At Saatzen and Istrup, on the table-land of 

 Paderborn, the carbonic acid rushes with great 

 force from a thousand ventholes in the ground. 

 In a swampy place near Istrup, mounds of mud, 

 from fifteen to twenty feet in height, and at least 

 a hundred feet round, have been thrown up by 

 these gas-streams : and on their surface there are 

 numberless little basins or pools, in which the 

 water is always kept in a state of violent agitation 

 by the rising of large gas-bubbles. In the valley 

 of the Brohl, in the Eifel, a single gas-spring 

 gives off daily about five thousand cubic feet of 



