95 



place, and the chlorine is nascent, the hydrogen of the ammonia, 

 from its very strong affinity for chlorine, seizes on a part of it, 

 and hence the ammonia is decomposed, and we have chlorhydrie 

 acid and nitrogen set free. 



The large quantity of carbonic acid gas contained in these 

 waters I look upon as derived from the decomposition of vegetable 

 matter within the earth, Avith the addition perhaps of a small 

 quantity derived from the decomposition of the bi-carbonate of 

 soda, as before mentioned, but no doubt the source is mainlj'- 

 from above, not from below, for there is a remarkable instance of 

 this in the waters of Spa, in Belgium, which evidently deiive 

 their source from a peaty moor at a considerable altitude above 

 the village. These waters are highly carbonated, and the greater 

 the heat of the weather, and consequent increase of vegetable 

 decomposition going on, the more are the waters supplied with 

 carbonic acid gas ; to so great an amount does this vary that the 

 gas is seen bubbling up quite rapidly in warm weather, and forms 

 a sort of weather glass to the natives. Sulphuretted hydrogen is 

 given off both by the coal itself, and is formed also where there is 

 a supply of sulphate of lime in meteoric water in the jjresence of 

 organic matter decaying ; in this latter case the organic matter 

 depriving the sulphate of lime of a portion of its oxygen, the 

 sulphuretted hydrogen thus formed, vdW, if the water contaming 

 it be of a considerable heat, be given off in the state of gas, and 

 we thus find it in springs of high temperature like Aix la Chapelle ; 

 Init if the heat is not considerable, the sulphuretted hydrogen 

 absorbs oxyj^en and passes on into the state of sulphuric acid 

 and this action is specially favoured by the presence of porous 

 Ijodies, and this formation of free sulphuric acid I take to account 

 for the presence of sulphate of soda in our waters, there being 

 lii-carbonate of soda left from the decomposition just mentioned. 

 When vegetable matter — wood — (which may be looked on chemi- 

 cally as coal plus hydrogen and oxygen), decays, it may lose part 

 of ifs carbon oxj'gen and hj'drogen as carbonic acid and car- 



