PEALE.] 



THEEMAL SPRINGS OF THE AZORES. 



337 



the northern one, with its thirteen volcanoes. Farther southward are 

 the Azores, then the Canary Islauds, south of which are tlie Cape Verde 

 Islands. These all lie on the great submarine ridge which divides the 

 Atlantic into two basins. On this ridge, according to Judd, there are 

 forty active volcanoes, three of them being submarine. One of the latter 

 broke out south of the Cape Verde Islands in 1824. The springs of 

 Iceland have already been described in Chapter I. We have the Azores 

 yet to mention. 



With the African springs I have also included those of the islands 

 of the Indian Ocean, Madagascar, the largest, being in such close prox- 

 imity to the African continent as to be best considered here, and the 

 islands of St. Paul and Amsterdam being small and unimportant. 



THE CALDEIRGS OR BOILING FOUNTAINS OF THE AZORES. 



The Azore Islands, as we have just mentioned, mark one of the vol- 

 canic centers of the Atlantic Ocean Eidge, and we are not, therefore, 

 surprised to find in them hot springs, such as are seen in the valley of 

 Furnas, in the island of San Miguel or St. Michael's; this island has 

 been the most disturbed by earthquakes. Hot springs are found in all 

 l^arts of the island, but especially in two places at the west end, in the 

 valley just mentioned, wMch is almost circular, a,bout 12 miles in cir- 

 cumference, surrounded by volcanic mountains. Through it flows the 

 Eibeira Quinte or Warm Eiver. The springs, which are of high tem- 

 perature and include some that spout to the height of 12 feet, are at one 

 end of the valley, surrounded by deposits whicb are mainly siliceous sint- 

 ers, white in color, streaked with reds, browns, and yellows. Sulphur 

 covers the ground in some places, and there are blue mud springs. One 

 group of springs is at the lake, which is 3 miles in circumference, and 

 the other is close to the town of Furnas. The water is described as 

 being bluish. At one place there are half a dozen jets in an acre of 

 ground. The siliceous sinter from here was analyzed by Dr. Webster, 

 and named Michaelite.* 



A pumping sound is heard all the time from the boiling pools and 

 steam holes. Wherever the water flows and evaporates, the siliceous 

 sinter is deposited. It resembles that from Iceland, and surrounds the 

 basins of the springs in rims 8 to 10 inches in height, as in the case of 

 so many of the Iceland, New Zealand, and Yellowstone hot springs. 



Dr. Webster gives the temperatures of fifteen springs, the lowest of 

 which is 73^* F., and the highest 207° F. Dr. Bullar gives the highest 

 temperature as about 212° F., and the following list of the principal 

 springs is made up from his description.-!- Thompson gives 194 as the 

 highest temperature : 



Name. 



Tempera- 

 ture. 



Kemarks. 





Y. 

 212 



105 



The water is opaline, and gives off sulphnreted hydro- 

 gen, boiling to the height of 3 or 4 feet. The hasin is 

 circular, 10 feet in diameter, and the deposits are 

 siliceous. 



A carbonated chalybeate -water. 



A caldron of boiling blue mud. 





















*Amer. Jour. Sci. and Arts, first scries, Vol. Ill, p. 'A91. 



tA winter in the Azores and a summer at the hatha of the Furnas, by Jos. Bullar, 

 M. D., and Henry Bullar. 



22 H, PT II 



V 



