HOT SPRINGS in ICELAND. 131 



of various colours, and beautifully veined, refembling a va- 

 riegated jafper. The heat may poflibly proceed from a fer- 

 mentation of the materials compofing thefe mounds ', but more 

 probably (I mould conjecture) from the fprings and fteam forced 

 up through them. The fprings muft have acquired their heat 

 at fome greater depth, from fome conftant, fteady caufe, (how- 

 ever difficult to explain), adequate to the length of time they 

 have been known to exift, with the fame unvaried force and 

 temperature. 



Springs do not boil on or near thefe banks only. They 

 rife in every part of the valley, and within the circumference of a 

 mile and an half, more than an hundred might eafily be counted* 

 Moft of them are very fmall, and may be juft perceived fim- 

 mering in the hole from whence the fteam is iffuing. This, 

 trailing on the ground, depofits in fome places a thin coat of 

 fulphur. The proportion varies ', for near fome of thefe fmall 

 fprings, fcarce any is perceptible, whilfl the channels by which 

 the water efcapes from others, are entirely lined with it for fe- 

 veral yards. Neither the water, nor the fteam from the larger 

 fprings, ever appear to depofit the fmalleft proportion of ful- 

 phur ; nor can the fulphureous vapour they contain be difco- 

 vered, otherwife than by the tafte of what has been boiled in 

 them for a long time. 



Many fprings boil in great caldrons or frafons, of two, three 

 or four feet diameter. The water in thefe is agitated with a 

 violent ebullition, and vaft clouds of fteam fly off from its 

 furface. Several little ftreams are formed by the water which 

 efcapes from the bafons ; and as thefe retain their heat for a 

 confiderable way, no little caution is required to walk among 

 them with fafety. 



The thermometer conftantly rofe in thefe fprings to the 212th 

 degree ; and in one fmall opening, from whence a quantity of 

 fteam ifTued with great impetuofity, Dr Wright obferved the 

 mercury rife, in two fucceflive trials, to the 213th degree.' 



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