4 DR. DAUBENY ON THE QUANTITY AND QUALITY 



that on an average the volume of gas evolved differed between one minute and others 

 as 12 to 20, or about one third, whilst the extreme variation was as 3 to 20, or 

 four times as great. 



By comparing together periods of five minutes, the difference between one obser- 

 vation and another will be found greatly reduced, the greatest variation being no 

 more than as 14 to 20, the mean only 19 to 20, as I have calculated by referring to 

 my original notes, and taking at hazard eleven observations, each extending to ten 

 minutes, and comparing the amount of gas obtained in the former half with that in 

 the latter half of the time. 



I conceive, therefore, we may be warranted in calculating, on the above data, that 

 no less than 223 cubic feet of gas are usually disengaged in the space of twenty-four 

 hours from this source alone ; and, large as this amount may appear, we have positive 

 testimony* that it was as constantly taking place almost a century and a half ago ; nor 

 is there much reason to doubt that it may have continued in an equally unintermitting 

 flow from the earliest periods at which the springs were known : the analogy, indeed, 

 of other thermal waters leading us to conclude, that the evolution of gas is a phe- 

 nomenon as intimately connected with the constitution of the waters as the presence 

 of a definite quantity of certain saline ingredients, or the possession of a particular 

 temperature ; both which, it is probable, continue unaltered during periods, histori- 

 cally speaking, of long duration. 



Dr. Clarke has shown -}-, that the hot springs which gush out from the foot of the 

 limestone precipices of Mount (Eta at the pass of Thermopylae, retain at this moment 

 a temperature of 1 1 1°, which probably is as high as that belonging to them in the times 

 of ancient Greece ; and, what is more to the point, the boiling up of gaseous bubbles, 

 which this traveller ascertained to be owing to the escape of sulphuretted hydrogen 

 from the springs, would seem to be noticed by Sophocles, who, if we adopt Dr. 

 Clarke's ingenious interpretation of the passage referred to|, makes a poetical use 

 of the phenomenon in his Trachiniee. 



Thus, too. Dr. Holland detected, at a spot on the coast of Albania, the escape 

 of carburetted hydrogen, probably on the precise spot where the ancient writers 

 describe a Nympheum, or a place where, owing to this cause, a perpetual flame was 

 observed to rise ^ : and the baths of Bithynia, described by a poet of the time of 



* GuiDOT, who wrote on the Bath waters in 1 696, speaking of the ochreous sediment thrown up hy the 

 spring, says : " ochra hie cum scaturigine regia erumpens jugiter, perenni ebullitionis motu, ita elaboratur, ut 

 tabulis affixa pictoriam semuletur." 



t Travels, vol. iv. p. 248. 



X He causes Deianira to relate, that some of the wool stained with the blood of the Centaur Nessus, falling 



upon the Trachinian plain, in a place where the sun's rays were the most fierce, there boiled up from the earth 



frothy bubbles. , „ 



eK ce yi]s, vaev 



TrpovKeir, oVa^eovon Opofxftwleis afpoi. — SoPHOCLis Trachiniae, vers. 701. (Ed. Brunck.) 



§ See Holland's Travels in Greece and Albania, 



