26 Proceedings of the Royol Physical Society. 



not be fouled by overstocking, and where practicable should 

 be broken up, drained, manured with such agents as salt, lime, 

 soot, and sulphate of iron, and stocked for upwards of two 

 years with animals of a different species ; and that " feg " or 

 rough grass should be destroyed by burning. 



III. Process for the Estirfiation of Colour in Water. By 

 J. Falconer King, Esq., City Analyst, Edinburgh. 



During the later months of the year 1873 and the spring 

 of 1874, I had occasion to examine and report upon many 

 samples of water, chiefly in connection with the water supply 

 of Edinburgh. 



As is well known, there were several schemes proposed for 

 the supply of the city, and samples of water from most of 

 them were submitted to me for examination. 



The analyses, as usually performed, showed all these waters 

 to be very much alike, because the main and almost only 

 difference between them was the extent to which they were 

 coloured. By the ordinary mode of analysis hitherto in 

 general use, this most important feature would either not 

 have been described at all, or would have been described in 

 language so vague as to be totally unintelligible. We find, 

 for instance, in many reports of analyses of water, the colour 

 stated as being much or little, or by some meaningless or 

 incomparable terms, as yellowish or brownish, which are 

 altogether without significance, as no one can tell with pre- 

 cision what is wished to be indicated by such vague expres- 

 sions, and which preclude the possibility of comparison, or of 

 the character of the water being accurately recorded, as that 

 tint which one observer would consider as fairly characterised 

 by one name, might quite possibly, and would indeed most 

 probably, be in the opinion of another, deserving of quite a 

 different appellation. In addition, therefore, to the usual 

 details set forth in reports of water analyses, I found that in 

 order to permit of the merits and demerits of these different 

 waters being properly discussed, compared, and recorded, it 

 would be necessary to have the depth of colour of each exactly 



