400 JOURNAL OF THE PLYMOUTH INSTITUTION. 
in three clays, the remainder keeping in suspension, and sticking 
against the sides of the vessel ; half per cent, in distilled water 
only cleared after remaining in rest for fourteen days. This 
accounts for its presence so far down the northern shore of the 
harbour, where the ebb is the slackest, all the grosser particles 
being deposited in the more immediate settling-bed formed by the 
Upper Laira. 
The magnitude of this latter settling is appreciated when it is 
borne in mind that the yearly quantity of sand removed by barges 
for building purposes must be from 50,000 to 100,000 tons. Not- 
withstanding this annual removal, the deposit is increasing, 
especially with china-clay, and barges now occupy double the 
time in " getting " a cargo of clean sand to what they did formerly. 
Such is the testimony of barge-masters ; but I will at present 
express no opinion on this important matter, as I have made no 
surveys or experiments so far up the estuary. 
How long this sand-silting has been going on is, of course, un- 
known ; but that at one time silt must have been deposited at a 
rapid rate, is evident from the appeals made to Parliament in 
Henry VIII. 's reign by West-countrymen, "to acte concernyge the 
amendynge and mayntenaunce of the havens of Plimouth, Dart- 
mouthe, Teygnmouth, Falmouth and Fowey, in the counties of 
Devonshyre and Cornewall, piteously sheweth and complayneth 
unto the kynge our soveraigne lord, and to the lordes spiritual and 
temperall and the Commons in this presente parliament assembled 
. . . for where before this tyme all the maner of shyppes being 
under the portage of 800 tonnes resortynge unto any of the sayde 
portes or havens myght at the lowe water easely enter in to the 
same and. there lye in suretie, what wynde or tempeste so ever 
dydde blowe . . . whiche sayde portes and havens been at this 
presente tyme in maner utterly decayde and clestroyde by meanes 
of certayne tynne workes called Streme workes used by certayne 
persones within the sayde counties, whiche persones more re- 
garclynge theyr owne private lucre than the commonwelth and 
suretie of this realme, have by workynge of the sayde streme 
works, dygging, serchynge and washyiige of the same .... con- 
veyed by the force of the sayde ryvers a mervalyous great 
quantite of sande, gravell, stone, robell, erthe, slyme, and fylth, so 
filled and choked the same that nowe a shyppe of a hundred can 
scantly entre at the halfe fioude to the decay e and utter destruction 
