170 OBSERVATIONS ON 



cause and effect is soon found. When the wind is in the 

 south-west, the barometer is low ; it may fall, for example, 

 from 30*25-29*25, i.e. 1 inch, which means the loss of about 

 J lb. pressure on the square inch ; or if a more sudden fall 

 to 28'25 is reached, there is a loss of 1 lb. to the square 

 inch, and less pressure is therefore suddenly exerted upon 

 the outflow of the spring. The force or energy producing 

 the spring, be it hydrostatic or atmospheric, is indirectly 

 affected by this loss of pressure on the outflow, inasmuch 

 as the change of atmospheric pressure is not conveyed 

 through the interstices of the earth and strata down to the 

 source or genesis of the spring in anything like the same 

 ratio that it affects the outlet of the spring, and vice versa 

 with a rise in the barometer the reverse takes place. In 

 coal mines and other shafts, where it is a matter of 

 equilibrium, apart from latent or accumulated energy in 

 the gases themselves, differences of atmospheric pressure 

 act in a similar way in releasing or holding back gases, 

 since barometrical changes are there more quickly felt than 

 at greater depths in the bowels of the earth. 



The behaviour of springs both in the surface and in 

 wells varies very much in their yield and mode of issue, 

 and also varies chemically, being either hard or soft, ac- 

 cording to the strata through which they pass, and yielding 

 constituents which often in themselves are useful for par- 

 ticular purposes. For 'instance, we have waters which con- 

 tain a good deal of carbonic acid gas and others which 

 absorb more freely carbonic acid gas (useful to mineral 

 water manufacturers), and, again, the waters which have 

 a large proportion of sulphates are much sought after by 

 brewers. This is one of the secrets of the good quality 

 and class of ales we get from the Burton Brewery, where 

 the water is derived from the sandstone wells, which con- 

 tain a large proportion of sulphates. 



