56 THE SILTING UP OF THE DEE: ITS CAUSE. 
How DOES THE TIDE COME IN? 
On December 4th, already referred to, the bore or head 
brought in three feet of water in less than five minutes, and in 
ten minutes there were four feet, which increased to nine feet in 
37 minutes. The tide still continued to slowly flow for one hour 
and eleven minutes longer, only making, however, seven inches 
increase in depth. The total flow was an hour and 48 minutes, 
and the total depth of water brought in was 9 feet 7 inches. It 
follows, therefore, that the total rise for the first ten minutes 
was four feet, in 27 minutes more to nine feet, and in the next 
hour and eleven minutes only'seven inches. There was a big 
fresh in the river for the tide to overcome, and a gale from the 
north-west assisting it to flow. 
How DID IT Go our? 
I took the depth three hours and fifty minutes after the tide 
turned, and it had only run out or fallen four feet ten inches. 
So that out of the nine feet of tidal flow which came up the 
river in 37 minutes, only four feet ten inches had returned in 
three hours and fifty minutes after high water. You will notice 
also that four feet of water came in within ten minutes, while 
only four feet ten inches went out in three hours fifty minutes. 
THE PowER OF RUNNING WATER. 
Sir Charles Lyell, in his ‘‘ Principles of Geology,” states that 
the power of running water has been proved by experiment to 
be as follows:—A velocity of three inches per second at the 
bottom is stated to be sufficient to tear up fine clay, six inches 
per second fine sand, twelve inches per second fine gravel, and 
three feet per second stones the size of an egg. The bore 
travelled on December 4th 88 yards in 22 seconds, or at the rate 
of twelve feet per second, or four times as fast as a stream 
capable of tearing up stones the size of an egg. What a terrible 
effect this bore must have as it passes up the sandy bed of the 
Dee. 
THE ESTUARY. 
I have so far treated only of the Dee between Chester and 
Connah’s Quay, where it is artificially confined between embank- 
ments. I must, therefore, now briefly notice the phenomena of 
the tidal flow and ebb of the estuary. In May, 1875, I made 
a number of observations on the tidal action between Hilbre and 
Chester. I will select two examples. The first, the morning 
tide of May zoth, 1875. At 5-30 a.m. the tide guage registered 
at Hilbre 6ft. below old dock sill. It rose as follows:—The 
