Apparently, the only natural mineral impurities of water that are desirable within narrow limits are carbonate of lime (chalk) and common salt, the nutritive roles of which have been already discussed. The great objection to an excess of mineral substances in drinking water is that they have a hurtful effect on the stomach and intestines, either by their astringent or by their laxative properties. "Hard water undoubtedly produces a derangement of the intestinal canal, and sympathetically of the skin; the harsh staring coat of horses receiving hard water rapidly disappears when a softer water is supplied. The amount of hardness in water which will produce this derangement of the intestinal canal has not been accurately determined, but from eight to ten grains of lime per gallon has, in many cases, been found injurious" (Fred. Smith). I have never known a case of illness in a horse being caused by the drinking of ordinary hard water; although every horse I have ever owned or trained was watered almost exclusively on hard water. They were not watered thus, because I was prejudiced one way or the other; but because hard water is the usual drinking water for man and stabled beast, and what is good enough for the master is generally considered to be good enough for the horse. I am here, of course, speaking of ordinary spring or well water, and not of mineral waters, which are "spring waters containing so large a quantity of some ingredient as to have a decided medicinal action" (Bloxatn).

The production of a tendency to the formation of calculi (stones in the intestines, bladder, and elsewhere) has often been put down to the drinking of hard water by horses, although statistics are wanting to support the allegation. For instance, Fred. Smith states that "cystic calculi among animals, particularly sheep, have been attributed to the excessive hardness 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" (Bloxam). 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 magnesium 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, shows that the water contains a percentage of organic or mineral impurities which render it unfit for drinking. A slightly muddy shade from the presence of clay is no great objection; because clay consumed in small quantities by a horse does not injuriously affect his health.

6. It Should Not Be Artificially Warmed

When a horse is hot and tired from severe work and his temperature is consequently raised (p. 52), the best thing we can do is to give him a drink of cold water, which will have a more cooling effect on him than warmer water (p. 129), and his thirst, which is prompted by the requirements of his system, will be satisfied with a smaller quantity of it - a fact that will be a direct gain, if work has to be resumed. An experience of two winters in Northern Russia has shown me that the coldest water even in the coldest weather, is neither distasteful nor hurtful to horses. In that country, during winter, all the common horses, such as cab and cart animals, are habitually given icy-cold water, and no attempt is ever made to warm it for them. These horses, which lead a very rough life in every way, except that they are well fed, and get as much cold water as they choose to drink, keep in excellent health; although the Russian and foreign horses which are pampered in the stables of Russian gentlemen suffer a great deal from disease. The cab horses of St. Petersburg, even in the middle of the terribly cold winter, maintain remarkably good condition. London cab horses, as we know, lead a very laborious life; their drinking water is never warmed for them, and yet their organs of digestion keep healthy. Throughout my long life, which has been spent among horses in all kinds of climates, and in many different parts of the world, I have never known, heard, or read of a case of injury to a horse caused by the fact of the water he drank being cold. On the other hand, I have seen scores of cases of horses refusing to drink, because the water offered to them had been artificially warmed. The employment of any means that prevents a horse from quenching his thirst, or at least renders water more or less distasteful to him, can hardly fail to be prejudicial to his health - to say nothing of the cruelty. A practice which can fulfil no good end, and which is liable to do harm, should not receive our encouragement.