302 LIQUIDS. 



rapidly absorbed, what is taken at the meal may facilitate the 

 accretion of the gastric juice at the time it is required, an excessive 

 quantity must be avoided. But where persons are exposed to great 

 heat and are obliged to work with violent exercise, large quantities 

 may be taken; and then nothing is better than simple water, the 

 purer and softer the better, unless a little oatmeal be added. 



Water is the same substance, from whatever source it is 

 derived, whether from seas, lakes or rivers. When allusion is made 

 to differences between waters, it is really to various bodies mingled 

 with the water. Thus a water-analysis really means an analysis of 

 the foreign bodies held in suspension by the water. These foreign 

 matters are exceedingly small in all drinking-waters, but in sea- 

 water there is about one part of solid substance to thirty parts of 

 water. In common waters there are only about 16 to 20 grains in 

 70,000 grains, or a gallon of water. Common salt is dissolved in 

 three or four times its quantity of water; but carbonate of lime is 

 not dissolved in less than 20,000 times its quantity. Salt occurs 

 more or less in every drinking water, and is undoubtedly wholesome, 

 but inasmuch as sewage is highly charged with salt, any water in 

 which there is an excess is to be regarded with very great suspicion. 

 Many of the worst wells in cities have been resorted to by the public 

 and highly valued on account of their slight flavor of salt; the water 

 was, however, prejudicial to health. Thirty grains of salt to a gallon 

 of water improve it considerably for drinking purposes. The excel- 

 lences of water are purity, softness, the presence of air and carbonic 

 acid to give freshness, and of salt to make it tasteless, and to pre- 

 vent its ready contamination by lead. 



Water is sometimes soft and sometimes hard, according to the 

 appearance or non-appearance of soap bubbles when washing. 

 Generally speaking, the difference depends upon the carbonate of 

 lime held in solution; until this is exhausted soap-bubbles or lather 

 cannot be produced. There are degrees of hardness; thus a water is 

 said to have six degrees when a gallon consumes as much soap as 

 will combine with six grains of carbonate of lime. Hardness is due 

 to the presence of magnesia as well as lime. Carbonate of lime in 

 small proportion in drinking-water is not injurious to most persons, 

 since it is assimilated and aids in the formation of the phosphate of 

 lime in bones; it is therefore useful for rickety children. Hard 

 waters, however, are not only unpleasant in use and harsh to the 

 skin, but have a tendency to dry up the mucous membranes just as 

 they do the skin; hence they may arrest the digestion and cause 

 gout, stone, gravel and goiter in districts where they are habitually 

 taken. Persons may thus suffer from' drinking the waters of a dis- 

 trict; and on the other hand, if they have been accustomed to use a 

 water which contains a large proportion of carbonate of lime, they 

 may lose their health by drinking soft water. Attention should 

 therefore be paid to the quality of the water of a district by persons 

 selecting a residence; they may go where the water would be preju- 



