264 



Mr. A. B. Nortlicote on the Water of 



when possible, all the chlorine; but in the water taken above Haw- 

 ford Brook the sodium is insufficient to combine with the whole 

 of the chlorine, and the small excess of the latter which remains I 

 have combined with magnesium . In the other waters the chlorine 

 is insufficient, and a little sodium remains ; and this, together with 

 the potassium, I have considered to exist as carbonate, derived 

 from complex silicates by the action of carbonic acid. Perhaps 

 these might more probably be regarded as silicates dissolved in 

 carbonic acid; and it is possible*, as such solutions have the power 

 of dissolving aluminic silicates, that the alumina present in the 

 waters may have entered in this way. Silurian limestones may 

 have furnished the calcic and d agnesic carbonates with traces of 

 ferrous and manganous carbonates, and perhaps the trace of 

 phosphate which usually occurs in the waters, as this, from Forbes's 

 analysesf, is a constant element in these rocks. Since, however, 

 the phosphate does not appear in the water of February, which 

 is also free from nitrates, this constituent may have a more di- 

 rect origin in sewage. I have apportioned the nitric anhydride 

 to the ammonia and to the lime, as forming the most probable 

 combinations. The results thus arranged give the following 

 composition for the solid residue of the different specimens of 

 the water of the Severn : — 



Severn Water of 1866-67. 

 Table of assumed Salts calculated in 1000 parts of the Water. 





Water from imme- 

 diately above the 

 waterworks. 



Water 



from 



Bailey's 



Ferry. 



Water from 

 above Haw- 

 ford Brook. 



Water from 

 Bailey's 

 Ferry. 



April 12, 

 1866. 



July 23, 

 1866. 



Oct. 30, 

 1866. 



February 14, 1867. 



Chloride of sodium ... 

 Chloride of magnesium 



Sulphate of lime 



Nitrate of ammonia ... 



•0992 



•0596 

 trace 

 -0205 

 trace 

 •0089 

 •0054 

 •0627 

 •0348 

 •0040 

 •0102 

 •0353 



•1390 



•0695 

 trace 

 •0041 

 trace 

 •0077 

 •0024 

 •0689 

 •0436 

 •0020 

 •0080 

 •0248 



•0688 



•0710 

 trace 

 •0124 

 trace 

 •0108 

 •0136 

 •0692 

 •0388 

 •0030 

 •0130 

 •0241 



•0204 

 •0021 

 •0306 



•0083 



•0452 

 •0168 

 •0049 

 •0077 

 •0110 



•0362 

 •0299 



•0098 

 •0010 

 •0475 

 •0199 



•0082 

 •0082 

 •0125 



Phosphate of lime 



Carbonate of potassa... 



Carbonate of soda 



Carbonate of lime 



Carbonate of magnesia. 



Silica 



Loss on ignition 





•3406 



•3700 



•3247 



•1470 



•1732 



Residue obtained by "1 

 direct evaporation . J 



•3117 



•3461 



•3059 



•1421 , 



•1664 



* Bischof (Cav. Soc), vol. ii. p. 65 j and vol.iii. p. 89, 

 f Phil. Mag. S. 4. vol. xiii. p. 365. 



