180 REPORT— 1875. 



ox (Bos longifrons and Bos prhnigenivs). The level of the surface is very 

 uniform over the whole district, aud is below high water of equinoctial 

 spring-tides, the country, where exposed to the overflow of the tides, lacing 

 jirotected by an ordinary sea-bank of from 3 to 5 feet high. The flat margin of 

 grass land between the sea-bank and the edge of the water still continues to 

 be raised above the level of the enclosed land by the deposit from very high 

 tides. 



The mud spoken of is of an exceedingly light character, borne up and 

 down in suspension in the water as long as the mean velocity of ebb or 

 flow does not fall much below about 2^ feet per second. Whenever from 

 any cause the velocity is much reduced, the mud begins to form a deposit. 

 An analysis of this silt, and also of the upper and lower strata of the alluvial 

 bed through which the lower part of the Avon runs, has been kindly made 

 by Mr. \Y. W. Stoddart, P.G.S., and is as follows :— 



Top heel of Alluvium (Brotun Clay). 



parts. 



Clay 26-52 



Sand with small quantity of mica 28-14 



Carbonate of lime 15-11 



Sulphate of lime 4-41 



Protoxide and peroxide of iron 4-74 



Salts of sodium, magnesium, &c 1-65 



Organic matter 4-15 



lloisture 15-28 



100-00 

 Bottom bed (or Blue Silt). 



Clay 3-55 



Saud 31-71 



Carbonate of lime 33-84 



Sulphate of lime 4-69 



Peroxide of iron 2-63 



Soluble salts 1-29 



Organic matter 2-64 



Moisture 19-65 



100-00 



Tidal mud of Avon, talcenfrom recent deposit in "North Channel.'''' 



parts. 



Clay 22-i8 



Sand (viz. coarse 0-61, fine 1-04) 1-65 



Carbouato of lime 22-27 



Peroxide of iron 4-43 



Soluble salts 5-29 



Organic matter 2-13 



Moisture 41-75 



iWoo 



A strildng instance of the great amoimt of mud held in siispension in the 

 tide-water of the Avon, and the readiness with which it will, under favour- 



