'J 



bT 



258 Sulphw^ Lake of Campagna. 



tism, Dissins a short distance into the hill near the ruins of the Villa 



nt>'"c3 



of Lucullus, it is easy to perceive the presence of volcanic energy in 

 the hot vapors accompanied with sulphur which issue copiously from 

 the surface. The villa of Lucullus was entirely buried in lapilll and 

 volcanic ashes, proceeding as is supposed from a vent in the immediate 

 neighborhood ; but from which vent does not appear — evidently not 

 from the one now containing Lake Agnano, since that has not been 

 active in the historic period. 



In another cavity excavated in the hill near to the Grotto del Cane, 

 is an abundant flow of carbonic acid, accompanied as is said by am- 

 monia — but wc did not perceive any odor of this gas nor any deposit 

 of carbonate of ammonia or of sal-ammoniac on the walls of the 

 place. 



3. Sulphur Lake of 



The celebrated sulphur lake of the Campagna, near Tivoli, the 

 Aquae Albute of the ancients, still retains its interest to the geologist 

 as the most remarkable of all the thermal sources of Italy. Whether 

 we regard the constancy of the flow from it both of water and of gas, 

 the area of the lake, or the important part which it and similar craters 

 appear to have played in the formation of the travertine of the Cam- 

 pagna — we must admit ihat it is worthy of attentive consideration. 



In the days of Father Kircher this lake was described as being over 

 one mile in circuit. Now the lake is not over 500 or 600 feet in diame- 

 ter, and its area is constantly diminishing. The baths of Agrippa 

 which are now at a short distance from the shore, show the extent to 

 which this contraction has taken place in that direction, since they 

 were erected in the waters of the lake which were much esteemed by 

 the ancient Romans for their hygienic effects. These baths were fre- 

 quented by Augustus and enlarged by Zenobia ; the latter spent her Ro- 

 man servitude in Tivoli, and in allusion to this, they are still called 

 " Bagni della Regina," At present the waters are conducted from this 

 lake by a canal artificially cut in ihe travertine by Cardinal IppoHto 

 d'Esle, former governor of Tivoli, for a distance of two miles. This 

 canal is nine feet wide and four feet deep, and there is a constant 

 discharge of the surplus waters through it in a very rapid current — the 



volume of which is remarkable when we notice the small size of the 

 source. 



The strong odor of sulphuretted hydrogen announces the existence of 

 this lake a long time before the traveller reaches it. The water was 

 examined by Sir Humphrey Davy, who found it to contain one volume 

 of carbonic acid, and less than J volume of sulphuretted hydrogen. 

 Tracing the canal from where it escapes the *' Via Appia nova" up ^o 

 the lake, a mile and a quarter, the observer is much struck with the 

 copious escape of large volumes of gas from the whole surface of the 

 lake, which is such as to convey the idea of ebullition. A stone cast 

 into the water is soon followed by a very violent escape of gas, caus- 



ing the whole adjoining area to boil with great energy and a loud sound 

 of effervescence. The water is very clear, a slight milky or opaliae 

 appearance it has being due, as we thought, to the reflection of the 

 white sides and bottom of the lake. Its temperature is 80' F., and it 



