401- IvI. Descloiseaux's Physical and Geological Observations 



. 1 also availed mj'self of my visit to the Geysii' to make 

 some chemical experiments upon the water of this remarkable 

 spring, which it would have been difficult to render so con- 

 clusive with water carried to Paris. I paid particular atten- 

 tion to the estimation of the sulphuretted hydrogen, the odour 

 of which is very perceptible in the vapour which incessantly 

 escapes from the basin, and to ascertain whether the soda 

 contained in that water is in the caustic or carbonated state. 



The sulphydrometer of M. Dupasquier served me for the 

 first determination. On operating with necessary caution, I 

 found that one litre of water of the Geysir, perfectly limpid 

 and cooled, protected from contact with the air, to about 40°, 

 contained 2''<^*448 of sulphuretted hydrogen. 



To ascertain the state of the soda, we collected some water 

 in a well-stoppered bottle, acidulated it with some drops of 

 hydrochloric acid, and boiled it; the vapour, collected in some 

 lime-water, yielded a very perceptible precipitate. Mixed 

 with some ammoniaca! chloride of calcium, the water was not 

 rendei'ed perceptibly turbid ; it therefore does not contain 

 free carbonic acid. 



The presence of chlorine or of alkaline chlorides was like- 

 wise ascertained by means of nitrate of silver. 



To obtain a complete analysis of this water, I collected a 

 quantity in a flask with a drawn-out neck and closed it over 

 the lamp, and in glass botdes closed with a good cork stopper 

 covered with caoutchouc. 



The water of the first flask was employed to estimate the 

 carbonic acid combined with the soda; this determination 

 was made in the laboratory of tiie Val-de-Grace, where M. 

 Millon was kind enough to place at our disposal one of the 

 apparatus which he employs to estimate the carbonic acid in 

 organic analysis. A second operation, made comparatively 

 on water of the bottles closed with a caoutchouc stopper, gave 

 a result nearly identical with that of the first experiment. 



metres = 156,760 kilogrammes in the second case, on condensing upon 

 the lower part of the Geysir, might re-establish its primitive level. 



I have stated above that this level was re-established in about seven 

 hours, and that from that moment only a small quantity of water flowed 

 over after each of the detonations which took place every two hours. 



The deficit in the Geysir, after a great eruption, might therefore be 

 made good by a subterraneous disengagement of vapour, varying from 

 1807 kilogrammes to 2394 kilogrammes an hour. Now an ordinary steam- 

 engine, without coating or covering and working without pressure {sans cn- 

 veloppe et sans ditente, consuming five kilogrammes of pit-coal an hour, 

 expends about thirty kilogrammes of vapour by horse-power. We see 

 therefore that the present pha;nomenon of the Geysir requires for its 

 production, only a development of vapour corresponding to nearly that of 

 an engine of 700 horse-power, which gives an approximate idea of the 

 order of this phaenomenon. 



