320 On Spring and Fiver Water, fyc. 



equal quantities of spring-water, Rhone-water, and distilled 

 water ; and has invariably found that the result of the boiling 

 during the same length of time, and in the same proportion of 

 the dye-stuff, was of a deeper and more beautiful hue in the 

 spring-water than in the Rhone-water, and in this latter than 

 in distilled water. The quantity of the colour extracted 

 seemed to be in inverse ratio to the purity of the water used. 



It was only natural to infer that this interesting and remark- 

 able event was owing mainly to the presence of the calcareous 

 salts of the different specimens of water subjected to trial, and 

 it was not a matter of much difficulty to determine by direct 

 experiment to which of the salts contained in these waters the 

 effect was principally to be attributed. Accordingly, M. Du- 

 pasquier undertook a careful investigation of the subject. He 

 prepared solutions in distilled water of each of the salts con- 

 tained either in the waters of the springs, or of the Rhone, and 

 after having boiled each of the dyes previously examined in 

 distilled water, he observed the effect which the solution of 

 each of the salts produced upon these decoctions. After all 

 these experiments, of which the author furnishes a detailed 

 table, it most decidedly appears that the carbonate of lime is 

 the only substance which increases the intensity of the colour 

 of dyes ; that the sulphate of lime, the chloride of calcium, 

 and the sulphate of magnesia, are either inoperative, or only 

 more or less change the peculiar colouring properties of the 

 dye ; and, finally, that carbonic acid, when it acts — and it does 

 so only on a few colours — has only a trifling agency, slightly 

 lightening the shade. 



But not only does the carbonate of lime act upon the colour 

 by brightening its hue, but it also appears to facilitate its solu- 

 tion in water, for this solution is, upon its addition, effected 

 more quickly and in greater abundance. This result, we need 

 scarcely add, perfectly harmonizes with the practical experi- 

 ence of dyers, who reckon that to obtain a given hue, a fifth 

 less of the dye suffices when spring-water is employed instead 

 of river-water. 



In a final summary, in which he briefly recapitulates all the 

 considerations which point out the marked superiority of the 

 spring-water on the banks of the Saone to the Rhone water, as 



