Shannon
2 of the 6 encyclopedias on this shelf carry an entry for Shannon. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a large river in the W. of Ireland, and one of the finest in the British Islands. It has a length of 220 miles, and is divided into the Upper and Lower Shannon. The Upper Shannon, by far the longest and narrowest part of the river, rises in the mountains of Ulster, at the N. W. extremity of the county of Cavan from the Cuilcagh Mountains, and flowing S. enters and passes through Lough Allen, till, quitting the county of Leitrim, it flows S. and E. and S. W. to the town of Banagher, forming from this portion of its course the boundary between Connaught and Leinster. From Banagher the river has first a S. W. and then a S. course, till, a little above the city of Limerick, it divides into two branches, which, flowing round King's Island, the most ancient part of the city, unite below to form the Lower Shannon. From its rise in Cavan to its encircling the King's Island, the river has a length of 180 miles. In this course the river is greatly interrupted by pted by shallows, falls, and rocks. The Lower Shannon, from Limerick to the mouth of its estuary ry in the Atlantic, has a length of 40 miles and a breadth of from 1 to 7 miles; though the channel in places is obstructed by islands, rocks, and shoals. It has, however, good anchorage everywhere, and forms a harbor of refuge for ships against the force of W. gales.
Aiton's Encyclopedia (1910)
a river of Ireland. It is the largest river in the United Kingdom . It rises in the north central part of Ireland and flows in general south and southwesterly through several large lakes, becoming a tidal estuary at Limerick. The total length is about 254 miles. Several million dollars have been spent in improving navigation between Lough Allen and Limerick. The Shannon is connected with Dublin and other ports of Ireland by a system of canals. See Ireland ; Limerick
What Has Changed in the Last Century
Aiton's called the Shannon in 1910 "the largest river in the United Kingdom"; since the Irish Free State was established in 1922 it has flowed almost entirely through an independent Ireland, and only its uppermost reaches touch the border region. The biggest physical change came in 1925-29, when the Shannon Scheme dammed the river at Ardnacrusha above Limerick to build what was then one of the largest hydroelectric stations in the world, a project that founded the Electricity Supply Board and first brought power to much of rural Ireland. The canal and navigation works both accounts describe now carry pleasure cruisers rather than cargo, and the estuary Collier's praised in 1921 as a "harbor of refuge" is flanked by Shannon Airport, opened in 1945, and by deep-water industrial berths at Foynes and Moneypoint. The river's length is now usually given as about 224 miles (360 km), between the two figures the old entries offer.
Written for this edition, 2026.