1867.] and the Cholera. 323 



organic impurities ; still, by rendering efficient ablution and thorough 

 cleanliness difficult of obtainment, they doubtless indirectly affect 

 the health of communities supplied with waters in which they are 

 present in considerable quantities. 



The chief hardening ingredients in potable waters are the salts 

 of lime and magnesia. These salts decompose soap ; forming curdy 

 and insoluble compounds containing the fatty acids of the soap and 

 the lime and magnesia of the salts. So long as this decomposition 

 goes on the soap fails to produce a frothiness in the water, but 

 when all the lime and magnesia salts have been decomposed by the 

 action of the soap, the slightest further addition of the latter 

 produces a lather when the water is agitated ; but this lather is 

 again destroyed by the addition of a further quantity of the hard 

 water. Thus, the addition of hard water to a solution of soap — or 

 the reverse of this operation —causes the production of the insoluble 

 curdy matter above mentioned. Bearing this in mind, it is easy to 

 understand the process of washing the skin with soap and hard 

 water, which may be thus described : — First, the skin is wetted with 

 the water, then soap is applied ; the latter soon decomposes all the 

 hardening salts contained in the small quantity of water with which 

 the skin is covered, and there is then formed a strong solution of 

 soap, which penetrates into the pores of the skin. This is the 

 process which goes on whilst a lather is being produced in washing, 

 but now the lather requires to be removed from the skin ; how can 

 this be done ? Obviously only in one of two ways, viz. by wiping it 

 off with a towel or by rinsing it away with water. In the former 

 case, the pores of the skin are left filled with soap solution ; in the 

 latter, they become plugged up with the greasy curdy matter which 

 results from the action of the hard water upon the soap solution 

 occupying the pores of the cuticle. As the latter process of re- 

 moving the lather is the one universally adopted, the operation of 

 washing with soap and hard water is perfectly analogous to that 

 used by the dyer or calico printer when he wishes to fix a pigment 

 in the pores of any tissue. He first introduces into the tubes of 

 the fibre of calico, for instance, a liquid containing one of the in- 

 gredients necessary for the formation of the insoluble pigment, 

 this is followed by another liquid containing the remaining 

 necessary ingredients, the insoluble pigment is then produced 

 within the very tubes of the cotton fibre, and is thus imprisoned 

 in such a manner as to defy removal by subsequent washing. The 

 process of ablution, therefore, in hard water is essentially one of 

 dyeing the skin with the white insoluble greasy and curdy salts of 

 the fatty acids contained in soap. The pores of the skin are thus 

 blocked up, and it is only because the insoluble pigment produced 

 is white that such a repulsive operation is tolerated. To those, 

 however, who have been accustomed to wash in soft water, the 



