Geology and Natural History. 413 
Some general estimates have already been made by Professors 
Ramsay and Geikie of the quantity of mineral matter carried 
down in solution by the THames ; but the more exact data supplied 
to the Commission enables us to make some additions to previous 
results. Taking the mean daily discharge of the Thames at King- 
down by the Thames every twenty-four hours is equal to 3,364,286 
Ibs, or 1502 tons, which is equal to 548,230 tons in the year. Of 
this daily quantity about two-thirds, or say 1000 tons, consist of 
carbonate of lime, and 238 tons of sulphate of lime; while limited 
Proportions of carbonate of magnesia, chlorides of sodium and 
potassium, sulphates of soda and potash, silica and traces of iron, 
alumina and phosphates constitute the rest. If we refer a small 
portion of the carbonates, and the sulphates and chlorides chiefly, 
to the impermeable argillaceous formations washed by the rain- 
Water, we shall still have at least 10 grains per gallon of carbonate 
of lime, due to the Chalk, Upper Greensand, Oolitic strata, and 
Maristone the superficial area of which, in the Thames basin above 
Ingston, is estimated by Mr. Harrison at 2072 square miles. 
Therefore the quantity of carbonate of lime carried away from 
this area by the Thames is equal to 797 tons daily, or 290,905 tons 
annually, which gives 140 tons removed yearly from each square 
mile; or, extending the caleulation to a century, we have a total 
removal of 29,090,500 tons, or of 14,000 tons from each square 
e of surface. Taking a ton of chalk, as a mean, as equal to 15 
cubic feet, this is equal to the removal of 210,000 cubic feet per 
century for each square mile, or of +, of an inch from the whole 
Surface in the course of a century, so that in the course of 13,200 
years a quantity equal to a thickness of about 1 foot would be 
temoved from our Chalk and Oolitic districts. 
8. Correlations of the Coal Measures of Britain, France and 
Belgium. From the Annive Address of the President of 
the Geological Society, Joseru Presrwicu, F.R.S., February, 
1872.—It may be asked if any correlation can be established be- 
tween the coal measures of Bristol and South Wales, and those of 
i 
ing mass of from 2000 to 3000 feet of rock called Pennant exists 
in both the Welsh and Bristol coal field; and the total mass of 
Coal-measures is not very different, it being, say, 10,500 feet in the 
one, and 8500 in the other, and there being in Wales 76, and in 
Somerset 55 workable seams of coal. In the Hainaut (or Mons 
