314 On Spring and Biver Water, as 



bicarbonate of lime will excite the digestive functions, as 

 does the bicarbonate of soda, in water, and other vehicles. 



Respecting hurtful substances, the most common is gypsum, 

 or sulphate of lime, which curdles a solution of soap, hardens 

 vegetables, and renders digestion painful and difficult. The 

 chloride of calcium and the nitrate of lime have the same 

 hurtful properties. 



Organic substances arc so difficult to demonstrate by the 

 use of chemical tests, that we must not always conclude from 

 the absence of appreciable characters diluted by this agency, 

 that the Avater is pure. On this point, the author mentions a 

 fact which was observed at Lyons, in which the use of a well 

 whose waters, on analysis, shewed nothing remarkable, in- 

 duced an endemic disorder in the garrison, and which ceased, 

 as soon as they were discontinued. Experiments, therefore, 

 in such cases, must be tried ; and if, as a general rule, the 

 water of ponds and marshes should be at once rejected, still 

 more anxiously should we abstain from those whose use ap- 

 pears to injure the health of the inhabitants who live in the 

 neighbourhood. 



As it regards the arts, that water is usually considered 

 unobjectionable which is esteemed a good drinking water ; 

 but, moreover, certain considerations should be kept in view, 

 depending upon the particular art in which it is employed. 



In dyeing, for example, clearness is an essential quality to 

 the purity of colours, and especially of the more delicate hues. 

 It has been remarked at Lyons, that those white silks which 

 arc prepared with the river-water are inferior, as to bright- 

 ness and purity, to those which have been bleached with 

 spring-water. It is also regarded as indispensable that the 

 water intended for bleaching, should not contain too great a 

 quantity of calcareous salts ; as then they will cause the soap 

 to curdle, and thus not only will occasion waste, but these 

 flakes, by attaching themselves to the silk, wool, or cotton, 

 will hinder the bleaching of the parts which are thus enve- 

 loped, and render the influence of the soap incomplete. 



One remark made by the author is alike curious and inte- 

 resting : it is, that the carbonate of lime held in solution in 

 water, in those proportions in which it is found in good drinking 



