THE BASIN OF THE THAMES. 



149 



reo-ulator upon the volume of the river, for whilst the rain which falls upon 

 impermeable rocks is quickly carried off, that whicli percolates through permeable 

 soil is stored up for months before it finds its way into the river. Curiously enough, 

 the labour of man has been expended to interfere with the natural discharge of the 

 river, and the Thames, which is by nature most inoffensive, has become a source 

 of danger and annoyance to the people who dwell along its banks. The locks, 

 which to the number of thirty -three, interfere with the natural discharge of the 

 river between Oxford and Teddington, are for the most part under the control of 

 millers, whose interests run counter to those of navigation and of the inhabitants 

 generally. They have reduced as far as possible the number of locks required for 

 raising the barges from one level to the other, and they take care to maintain the 

 level of the river at its highest, so as to secure ample motive power, quite regard- 

 less of the fact that by doing so they expose the riverine regions to disastrous 



Fig. 81. — Old London Buidge. 



inundations. The channel of the river being thus for the most part bank-full, is 

 incapable of receiving the surplus water resulting from exceptional rains, and floods 

 are the natural consequence. But what matters this to the millers, who appear to 

 be guided by the axiom that " one man's loss is another man's gain ?" 



But whilst the normal régime of the Upper Thames is being interfered with by 

 locks, the channel exposed to the action of the tide was, until recently, quite as 

 much encumbered by old-fashioned bridges. Old London Bridge, owing to its 

 contracted arches, proved a formidable impediment to the free passage of the tide. At 

 low water, on account of the obstacle it presented to the returning tide, there was a 

 fall here of about 5 feet. Since the reconstruction of this bridge a greatly increased 

 body of tidal water flows up and down the river, and as it meets with no obstruc- 

 tion, it flows with a decidedly greater velocity. The effect of this is to scour and 

 deepen the channel ; shores formerly foul and muddy have become clean shingle 

 and gravel ; the time of high water is an hour in advance of what it was at 



