Of the embouchure of the Ribble into the Irish Sea, 182 m.
When the motion is reversed and the air moves out of the pipe at the embouchure, the sheet is deflected on to the outer side of the sharp edge, and no work is done against it by the air in the pipe.
The only other tributary of any size that the sea receives is the Jaxartes (Sihun, Syr-darya) which enters towards the northern extremity of the east coast, and is suspected to be shifting its embouchure more and more to the north.
Its extreme length is about ioo and its breadth varies from 70 to over ioo m., but the exact limits are vague, and the modern signification of the name practically comprehends the peninsula formed by the lower Helmund and its embouchure on the one side and the Hamun (lake) on the other.
Outer Seistan, the country on the right bank of the Helmund, and east of its embouchure in the Hamun, extends more than ioo m.