4 VETERINARY HYGIENE 



Like surface water it contains more gas in solution than does rain 

 water, and in many instances it holds a considerable amount of 

 dissolved solids and is therefore hard. 



Artesian wells. If there is a pervious layer of soil between 

 two layers of impermeable strata its water will percolate to and be 

 held by the second or deeper impermeable layer. If the formation 

 of the land be that of a crater where the various strata run up to 

 the surface at a higher level than the bottom of the basin, the 

 water between the two impermeable layers will be held there under 

 considerable pressure. If, therefore, this supply be tapped by bor- 

 ing, the water will spout up the shaft or bore tube. Such is an 

 artesian well. The supply from these wells is sometimes enormous, 

 two or more million gallons being obtained daily from some of the 

 Australian wells. They are commonly sunk to a depth of 1500 

 feet, and may be much deeper. The water that issues from the 

 deep borings may have a temperature of over 100 F. 

 Artesian well water though pure often contains a high proportion 

 of dissolved solids. 



Springs. An outlet of water at the surface is called a spring. 

 A spring may result from a dip in the land cutting across an imper- 

 meable stratum, which thus appearing at the surface affords an 

 outlet to the water that has gathered on it. Such water is essentially 

 surface or ground water. It may be pure if the configuration of 

 the land is such that a considerable depth of soil covers the stratum 

 that holds the water. If, however, the soil is shallow, the water 

 will appear at the spring without having undergone sufficient filtra- 

 tion, and may therefore be impure. These " land springs," or 

 " dip springs " as they are commonly called, fail in periods of 

 drought and " break " again after rain. If they soon run dry 

 and soon break then they are shallow, and the water is of doubtful 

 purity. If, on the contrary, the flow continues during dry weather, 

 then the supply is a deep one. 



Springs also appear from a fissure occurring in a stratum 

 such as rock, thus letting the water underlying the rock escape. 

 These are called " fissure springs." The water is pure and similar 

 to that obtained from deep wells. Fissure springs are not liable 

 to fluctuation like land springs. Another form of spring results 

 from a geological " fault." A " fault " is where two strata of 

 different formations join with a fissure at the junction. The water 

 of a " junction spring," as it is called, issues at the fissure, and 

 may have come from a distance or be merely surface water. Its 

 character therefore depends upon the nature of the ground. 



Ice water. When water freezes a considerable amount of 



