3 ^ 
We must next consider the amount brought down by the 
river when in flood. For convenience sake, I have considered 
the river to be in flood when it is more than one foot above 
summer level. This is, of course, arbitrary ; but an arbitrary 
line must be drawn somewhere. The average height above 
summer level during the days on which the experiments were 
tried, was about three feet. This gives a daily flow of about 
4,500,000 cubic metres (24,500 cubic yards). This multiplied 
by the average amount brought down (at the rate of 211 
mgrmes. per litie) and by 221, the number of days in the year 
on which we have assumed the river to be under flood 
conditions, gives a total of about 209,839,500 kilogrammes, or 
about 206,092 tons. Adding this to the amount already 
obtained as brought down by the river when at summer level, 
we find that the river brought down during the year under 
observation 295,257,420 kilogrammes or 290,092 tons of solid 
matter in suspension and solution. 
These results are rough and approximate only, but they are 
founded on carefully conducted experiments and are under, 
rather than over, the mark. We must bear in mind, too, 
the fact that the year during which these observations were 
taken was an exceptionally dry one, unusually free from heavy 
floods. We may, therefore, safely say as a result of these 
experiments that the Ouse annually brings past York about 
300,000 tons of solid matter. 
This is equivalent to the removal of one metre per 7,000 
years from the surface of the Ouse basin as far as York—that 
is, the surface would lose one foot in 2,300 years. Assuming 
the planing down of the surface to be uniform over the Ouse 
basin, it would require 120,000 years to reduce the country 
round York to the sea level. As a matter of fact, the rate of 
waste is greater at high than at low elevations, and the period 
mentioned above should be doubled at least. 
H. M. PLATNAUER. 
