104 SPRINGS, HIVJ2RS, CANALS, LAKES, 



sort of ducks is cast out in great abundance, by the water gushing 

 out with much force.* 



[Pavasor, Phil. Trans. 16s;.] 



BUBBLING, TEPID, AND BOILING SPRINGS f. 

 1. Introductory Remarks. 



HEAT, water and vapours of various kinds, exist in prodigiou* 

 quantities beneath the surface of the e-.rfh; and frequently, as we 

 have already seen in the phenomena of \v!^:noes and earthquakes, 

 burst forth from enormous jaws or openings imd with tremendous 

 destruction. It often happens, however, that the openings are small 

 and porous, and that the heat or vapours that ascend through them 

 only asrrmi in a stale of union with water. And hence, that almost 

 infinite variety in the characters of those fountains and lakes that are 

 found to be combined with extraordinary materials. In some cases 

 the elastic passes or vapours ascend from specific le-vity alone, and 

 destitute of all taste and odour; and we have met with springs that 

 bubble without boiling, or betraying heat or any ether foreign 

 property. At other times, they are strongly impregnated with 

 heat; and are then either tepid or boiling, according to the pro- 

 portion of extricated caloric they contain. And occasional!}', 

 whether hot or cold, they are intermixed with metallic, sulphurous, 

 saline or other substances, and hence assume the name of mineral 

 waters : while if the substance thus dissolved be combustible, as 

 naphtha, bitumen or turpentine, the fountain will often inflame and 

 burn upon ilie application of a lighted torch. 



Upon this subject many of the observations offered by Dr. Tan- 

 -wed Robinson in the Philosophical Transactions, are worthy of at- 



* There is another, hut a less scieotific account of the same lake given in tlic 

 saftie journal, by Dr. Brown^ Vol. IV. year 1669. The reader will also meet 

 with other instances of ebbing and flowing waters in the ensuing sections; ami 

 ially in section x, Iiitroductoiy remarks ; and section xi. Lake Jezero* 

 I or other instance^ the reader may turn to the two ensuing sectioas* 



