Dr Daubeny on the Spring at Torre del Annunziata, 227 



acid gas which rises up through the same aperture. The vo- 

 lume of this is sufficient, to maintain the water itself in a state of 

 constant and violent ebullition, and to impregnate the air of the 

 stone cylinder through which it escapes, to such a degree, as to 

 render it absolutely unrespirable. 



The carbonic acid has also been long observed to rise in 

 bubbles through the sea-water near this spot, and I am assured 

 by Colonel Robinson, that there are patches of land upon the 

 cliff, upon which, owing to the disengagement of this same 

 noxious gas, no plants can be made to grow. A similar state- 

 ment with regard to other places within the precincts of Vesu- 

 vius, has been given long ago by Breislac. 



The disengagement of carbonic acid throughout this district 

 is indeed so well known to all who have visited Naples, and is 

 so obviously referable to the action of heat upon the contigu- 

 ous beds of limestone, that it does not seem to require in itself 

 any particular notice. 



It has not, however, I believe, been so generally remarked, 

 that, in almost every instance, there is a slight admixture with it 

 both of oxygen and nitrogen gases, in which, however, the for- 

 mer never, according to my experience, rises to the proportion 

 present in atmospheric air. 



This observation I have had the means of substantiating, not 

 only in the precincts of Vesuvius, but also at the Lago di Am- 

 santo amongst the Apennines, near Mount Vulture in Apulia, 

 and at the Lago di Solfatara near Rome. 



At the spring of Torre del Annunziata, after carefully re- 

 moving the carbonic acid, I found the residuary gas to consist 

 of oxygen 16, nitrogen 84 ; at the spring of Santa Lucia in 

 Naples, of oxygen 14.5, nitrogen 85.5 ; at the Lago di Amsanto, 

 of oxygen 9, nitrogen 91 ; at the Aqua Santa on Mount Vultur, 

 oxygen 10, nitrogen 90; at the Lago di Solfatara, near Tivoli, 

 of oxygen 9.5, nitrogen 90.5. I have not chosen to class with 

 the above the mineral water of Castellamare, in the Bay of 

 Naples, as in it the relative proportions of the carbonic acid, and 

 the residuary gas disengaged, approached so much more nearly 

 to an equality ; that collected by me consisting of carbonic acid 

 53.0, nitrogen 47.0, oxygen 0.5. 



With respect to the cause of nitrogen in springs, I do not in- 



