connected with Health and the Arts. 315 



waters, has not, like other calcareous salts, the property of 

 precipitating the solution of soap. M. Dupasquier attributes 

 this effect to the excess of carbonic acid, which hinders the 

 reaction of the calcareous carbonate upon the stearate and 

 oleate of soda, which form soap. He has proved this inte- 

 resting fact by numerous experiments, which he describes in 

 detail, and from which it results that there must be in water 

 a proportion of this salt almost six times greater than that 

 which exists in common spring water, before a sensible effect 

 will be detected in the solution of soap. Another important 

 remark is this, that for dyeing it is serviceable to employ water 

 whose inherent temperature remains throughout the winter as 

 far as possible from the freezing point. In this state it is more 

 active in its dissolving powers, both in washing and bleaching, 

 and also in removing the soluble colours which are intended 

 to be retained by means of a mordant. The influence of the 

 calcareous salts contained in water upon colours is remark- 

 able. They heighten their intensity without altering their 

 freshness and tint. Hence the dyers at Lyons prefer spring- 

 waters, and ascribe to their virtues a considerable diminution 

 of the required dyes. It is striking that they have no such* 

 influence upon the different shades of black, and that the soft- 

 est waters are accordingly preferred for this hue. 



In the following chapters, the author compares the advan- 

 tages and disadvantages accruing to Lyons from the employ- 

 ment of the water of the Rhone, and that of the springs whose 

 properties he has so carefully examined. He does not hesi- 

 tate to give the preference, as it regards clearness, to the 

 spring-water, for it has it in perfection ; whilst the water of 

 the Rhone, after ten days' repose, has not deposited all its se- 

 dimentary matter ; and none of the known systems of infiltra- 

 tion can effect, without enormous expense, a sufficient purifica- 

 tion of the 1,500,000 or 2,000,000 gallons of water, which the 

 city requires. The author has even remarked that the Rhone 

 water, filtered in an apparatus at the Great School, contains 

 more earthy salts than the water taken from the stream, and 

 filtered through paper. Hence, it is probable that in the pres- 

 sure employed in the operation, the earthy matters which are 

 deposited become more soluble. The foreign matter which 



