16 SILTING UP OF THE CREEKS OP FALMOUTH HAVEN. 



Caenon Creek, the next in order, shows the most serious 

 accumulation of silt in Falmouth Haven. 



The river flowing at Carnon Bridge takes the drainage of 9510 

 acres, and that of Perranwharf of 9190 acres. It has been cal- 

 culated that the former stream discharges on the average about 

 1,140,000 cubic feet per day, and about 980,000 cabic feet from 

 the great adit, giving a total quantity of about 2,120,000 cubic 

 feet per day, and this amount is highly charged with silt in 

 suspension from the mines and stamping mills. 



In a chart of Falmouth Harbour drawn about 1620, the tide 

 is shown flowing beyond Lower Carnon, and there is a tradition 

 that it once flowed above Bissoe Bridge, but a very different 

 condition of the river obtains now. 



In the 21 years between 1821 and 1842, about 16,416,000 

 cubic feet of silt were deposited between Higher Carnon and 

 Devoran, besides a large quantity below. 



The depths silted up at different points varied from 2| feet at 

 Carnon Bridge, to 9 feet at a spot TiOO yards below the new 

 turnpike road, and on the average is about 5^ feet, giving 20 feet 

 accumulation in 100 years, or 1 foot in 5 years, during this period, 

 which was during a time of great activity in the mining districts. 



Mr. W. J. Henwood, F.R.S., stated in his presidential address 

 to this Society in 1870, that at Higher Carnon a foot bridge 

 which in 1815 to 1820 was three to four feet above the level of 

 the stream, in 1867 had been buried under about two feet of 

 detritus, the surface of the valley at this spot having been 

 raised at the rate of about one foot in ten years. 



Nor has the mischief been less below Devoran. Mr. Eichard 

 Thomas, writing on the subject in his history of Falmouth, says : 

 '■' If these waters be charged ordinarily with 1 part in 300 of 

 earthly matter (sometimes they contain more than double that 

 quantitv) there will be brought annually into Eestronguet creek 

 about two millions and a half of cubic feet .... besides immense 

 quantities of gravel which in times of heavy rain, are swept 

 along the Vjeds of the streams and ultimately into the navigation." 



It would be, therefore, expected that this arm of the Haven 

 should have shoaled considerably, and this is seen to be the case, 

 for on referring to the Admiralty Survey of 1698, it is found 

 that the channel opposite PenpoU has silted up 10 feet, and at 

 Eestronguet Pool, at the higher end, where there was in 1698 



