The expenditure on the river up to 1878 was 800,738_l._ The average cost of maintenance was 3300_l._, and the total receipts from tolls during the previous five years was 9510_l._, being an average yearly receipt of 1902_l._ This sum, deducted from the average expenditure of 3300_l._, left a net yearly loss of 1398_l._ At this average rate for the previous thirty years the money loss by the Shannon navigation amounts to 41,940_l._ The depth of water for this navigation, over 7 feet to 10 feet, is maintained by eight wholly immovable weir-mounds. These weir-mounds cause inundations, damaging 24,000 acres of land. This damage during the last thirty years amounts to more than 100,000_l._ In the section between Limerick and Athlone, 68 miles, the average receipts of tolls for the five years ending 1878 was 1274_l._ Out of that sum an engineer and eighteen lock-keepers had to be paid 686_l._, together with repairs, which left from 300_l._ to 400_l._ a year profit. In the section above Athlone, about 80 miles, the average receipt of tolls in the same five years was 197_l._, against the annual expenses of repairs and the salaries of an engineer and ten lock-keepers, amounting to 385_l._ The interests of the Shannon drainage do not, in Mr. Lynam’s view,[58] require to diminish the minimum depth of water under 5½ feet on the lock sills. These interests require merely that the surface of the river and lakes shall be kept within a range of 5½ feet to 8½ feet on the sills of all locks from Athlone to Limerick. The bye-laws made by the Board of Works for the Shannon limit the draught of boats to 4 feet 10½ inches. The river and locks are maintained by the weir-mounds at levels that rarely are less than 7½ feet on the lock sills, and rise in floods to 9 feet.