The experiment was so far successful that, with incredible difficulty, the two vessels did actually reach Meskene, but the result of the expedition was to show that practically the river could not be used as a high-road of commerce, the continuous rapids and falls during the low season, caused mainly by the artificial obstructions of the irrigating dams, being insurmountable by ordinary steam power, and the aid of hundreds of hands being thus required to drag the vessels up the stream at those points by main force.
Precisely the same thing happens in the actual crust of the earth, except that, in the formations usually met with, the strata are so irregularly permeable that no such uniform percolation occurs, and most of the water, instead of oozing out near the sea-level, meets with obstructions which cause it to issue, sometimes below the sea-level and sometimes above it, in the form of concentrated springs.
Not only are the national and state governments forbidden by the constitution to establish or subsidize religious worship, but its freedom is guaranteed by a prohibition against placing obstructions upon its exercise.
Besides, it was declared a free imperial port in 1719, and was therefore released from the obstructions to trade contained in the hampering legislation of the period.
The bed of the great river maintains a fairly constant position between its extreme banks, but the channels within that bed are so constantly shifting as to require close supervision on the part of the navigation authorities; so much detritus is carried down as to form a perpetually changing series of obstructions to steamer traffic.
This weir retains the river above it at half-tide level, in order to cover the mud-banks which had been bared at low tide between Richmond and Teddington by the lowering of the low-water level, owing to the removal of various obstructions in the river below.
The improvement of waterways in the interior of the empire was not neglected, the Babylonian canal system was repaired, the obstructions in the Tigris removed.
Many of the Atlantic coast rivers would afford excellent port facilities if obstructions were removed from their mouths.
From 1904 onwards the French undertook works on the Niger between Bamako - whence there is railway communication with the Senegal - and Ansongo with a view to deepening the channel and removing obstructions to navigation.
Similarly the obstructions offered to water communication by interruption through land or shallows are overcome by cutting canals or dredging out channels.