136 WATERING HORSES. 



particularly sheep, have been attributed to the excessive hard- 

 ness of the water. Calculus disease is more common in the 

 limestone districts than any other." On the other hand, we 

 have the well-known fact that limestone districts are more 

 suitable for the breeding and rearing of good horses, than 

 districts which are poor in lime. The basis of limestone is 

 of course carbonate of lime. 



4. It should be free from any odour or unpleasant taste. Any 

 smell which natural water may possess will generally be caused 

 by the presence of decomposing organic matter. As a rough 

 test, we may " pour half-a-pint of the water into a wide-mouthed 

 bottle or decanter, close it with the stopper or with the palm 

 of the hand, and shake it violently up and down. If an 

 offensive odour is then perceived, the water is probably 

 contaminated by sewage gas, and possibly with other 

 constituents from the same source " (Bloxatn). Horses have 

 a very acute sense of smell, and consequently they will often 

 refuse to drink water which has been boiled, on account of its 

 having been smoked, even when the smell thus imparted is 

 extremely faint. Rain-water which comes off the roof of a 

 house often contains particles of soot, and in such a case 

 might be distasteful to a horse. 



Although, as we have seen, a small percentage of mineral 

 matter improves the taste of water ; an excess particularly 

 of common salt, iron, sulphate of lime, and salts of mag- 

 nesium and potassium will render it disagreeable for drinking 

 purposes. The sweetish taste communicated to water by 

 clay appears to be in no way unpleasant to horses, which is a 

 fact we can readily understand from our knowledge that grass 

 is often a good deal impregnated with clay. The presence 

 of decomposing organic matter gives a mawkish taste to 

 water. 



5. It should be free from any unusual colour or lustre. 

 A green or yellow colour, or an opalescent or slimy lustre, 



