DRINKING WATER. 133 



digestion by, among other ways, assisting the digestive juices 

 to permeate through the food that is in the alimentary canal. 

 The fact that this water is universally found by mankind to 

 be pleasanter to drink than water poor in gases, is a strong 

 proof that it is the more healthy beverage of the two. 

 Although from want of exact knowledge we cannot un- 

 reservedly extend this conclusion to horses, the probabilities 

 are all in favour of its being equally true in their case. 



The foregoing considerations suggest the sound practical 

 rule that it is better to give a horse fresh water, than water 

 which has been allowed to stand for some time after it has 

 been drawn, and that it should not be artificially warmed. If 

 a particular sample of water happened to hold a large quantity 

 of suspended matter, as might occur on rare occasions, it 

 might be necessary to let the solid particles settle down as 

 sediment, before giving the water to a horse to drink. 



The presence of carbonic acid gas in water increases the 

 solubility of carbonate of lime and may thus assist in 

 nutrition. 



3. // ought not to contain an excess of mineral matter, which 

 excess may be defined as a greater quantity than 4 j grains to 

 a pint of water. The Thames water which is supplied to 

 London contains about 2^ grains to the pint. The principal 

 mineral substances held in solution by river and spring water 

 are carbonates of lime, soda, and magnesia ; sulphates of 

 soda, potash, lime, and magnesia ; nitrates of potash, soda, 

 and magnesia ; chlorides of sodium and lime ; and peroxide 

 of iron. The chief mineral matters held in suspension are 

 clay and sand. 



Drinking water may be broadly classed as soft water, and 

 hard water, which is the term commonly applied to water in 

 which it is difficult to make a lather with soap. Hardness of 

 water is caused by a comparatively large percentage of mineral 

 matter being held in solution in that fluid, and may be divided 



