of Edinburgh, Session 1867 - 68 . 
315 
first two of these necessary conditions occur, viz., sufficient shal- 
low water and presence of sand, the sea, owing to the configuration 
of the coast, is so landlocked that waves of sufficient size to pro- 
duce the third condition cannot be generated, and hence in the 
Forth there is the phenomenon of a barless river. 
At the Danube, a large river, discharging in ordinary flood no 
less than twenty millions of cubic feet of water per minute, enters 
a tideless sea, and we have a totally different class of phenomena 
to deal with. The river brings down an amount of detritus which 
has been ascertained by Sir Charles Hartley to be equal to 27 cubic 
inches per cubic yard, and to be equal to no less, in cases of high 
flood, than 600,000 cubic yards of solid deposit in 24 hours. Like 
the Mississippi and the Nile, the Danube owes its extensive delta 
to the gradual accretion of this sedimentary deposit, and the bar at 
its mouth Is due to the same action. It therefore differs entirely 
from the bars in this country, as is well exemplified In the fact 
that, whereas in our harbours the bars are always deepest when the 
sea is calm and the rivers are in flood , and therefore most efficient 
as scouring agents, at the Danube the bar is, on the contrary, in- 
variably shallowest when the river is in flood, because it is then 
charged with a larger amount of deposit. 
Another feature of difference in the treatment of such a case as 
the Danube is to be found in the circumstance that there is no 
reversal of the current due to tidal influence, and therefore it is 
unnecessary, in fixing the direction of the piers, or indeed In de- 
signing any of the works, to provide for the admission of tidal 
water to act as a scour on its return to the ocean, a provision which 
always demands special attention in designing tidal works on our 
coasts. 
The works executed at the Sulina mouth consist of a north pier 
4640 feet in length, and a soutli pier 3000 feet in length, both 
built of pierres perdues surmounted by a timber staging, with an 
entrance between of 600 feet, and the slightness of their structure 
indicates the modified character of the waves to which they are 
exposed. 
The works, which are understood to have cost about £100,000,. 
are highly creditable to the talent and energy of Sir Charles Hart- 
ley, and have now been completed for five years, and their effect 
