220 



GEYSERS OF ICELAND. 



[Ch. XXXIII. 



At the moutli of this tube the water has a temperature 

 corresponding to the pressure of the atmosphere, of about 



212 



it is much I 

 xp crimen t 



meter 



suspended by a string in the pipe rising to 266'' Fahr. 

 or no less than 48° above the boiling point. After the 



emams 



and pipe is found to be much cooled. 



Previously to these experiments of Bunsen andDescloizeaux 

 made in Iceland in 1846, it would scarcely have been supposed 

 possible that the lower part of a free and open column of 

 water could be raised so much in temperature without causing 

 a circulation of ascending and descending currents, followed 



almost immediate 



Such circula- 



tion is no doubt impeded greatly by the sides of the well not 

 being vertical, and by numerous contractions of its diameter, 

 but the phenomenon may be chiefly due to another cause. 

 According to experiments on the cohesion of liquids by 

 Mr. Donny of Ghent, it appears that when water is freed 

 from all admixture of air, its temperature can be raised, even 

 under ordinary atmospheric pressure, to 275° Fahr., so much 

 does the cohesion of its molecules increase* when they 

 are not separated by particles of air. As water lono- boiled 



1 _ t5 



more and more 



he bottom 

 periments 



companion 



fluid filling the tube is constantly receiving accessions of hot 

 water from below, while it becomes cooler above by evapora- 

 tion on the broad surface of the basin. They also came to a 

 conclusion of no small interest, as bearing on the probable 



nam 



main seat or focus 



mechanical 



This was proved by letting down stones suspended by strings 

 to various depths. Those which were sunk to considerable 

 distances from the surface were not cast up again when the 

 next eruption of the Geyser took place, whereas those nearer 



* Sec Mr. Horner's Anniversary Address, Q„art. Journ. Cxeol. Soc. 1847, liii. 



&i' 



ss^^ 



ujoi 



e: 



the 

 Other 



It 



seeir 



tempera 

 0^ 



or 



force ^11 

 the e4'< 

 its pr-'' 



the nexl 



flash in- 

 ehullitic 



of the fi 



Yoleanlc 



cavities 



the ear 



^ater c 



these, tl 



force it 



cohimn 

 cases w 

 mixed 



ftat stc 

 and thi; 



1 



an 



a 



•"^ erup 



into (>; 



steam 

 belted 



1 



V th. 



<?r; 



oi-ig 







