Severn
2 of the 7 encyclopedias on this shelf carry an entry for Severn. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
the second largest river in England, formed by the union of two small streams which rise in Mount Plinlimmon, Montgomeryshire. It flows through Montgomeryshire, Shropshire, Worcestershire, and Gloucestershire, passing the towns of Newtown, Welshpool, Shrewsbury, Worcester, Tewkesbury, Gloucester, and Bristol, and after a cir cuitous S. course of about 210 miles falls into the Bristol Channel. It receives the Tern, Upper Avon, and Lower Avon on the left, and the Teme and Wye on the right. Its basin has an area of 8,580 square miles. It is navigable to Welshpool, about 178 miles above its mouth and 225 feet above sea-level. Below Gloucester its navigation is much impeded, but this has been obviated by a canal from this city to a point on the estuary 2 miles from Berkeley, capable of carrying vessels of 350 tons. Below Gloucester the banks become so low that destructive inundations have not infrequently occurred. These have been partly caused by one of the most remarkable features of the river, its bore, or by the height of the tides, which at the mouth of the Avon sometimes exceed 48 feet, and at Chepstow attain even 60 feet. A railway tunnel 42 miles long has been driven below the river from near Avonmouth, in Gloucestershire, across to Monmouthshire, and a railway bridge, 3,581 feet long, crossing the river at Sharpness higher up.
Aiton's Encyclopedia (1910)
a river of England. It ranks second to the Thames in length and importance. It rises in Wales and empties into the Bristol Channel. Worcester and Gloucester are on its banks. See Avon ; Bristol