58 Proceedings of the 



few tributaries from the drainage of the district through which it passes, 

 and consequently it is little influenced by excessive rain either by increasa 

 of volume or discolouration. In connection with the Wandle, reference may 

 be made to the Bourne from the Caterham Valley. Some of our frienda 

 present will have heard of and several have seen the Bourne, which after 

 wet seasons in the autumn, bursts forth about March in the Caterham 

 Valley, and runs into and down Smitham Bottom, parallel to the Brighton 

 Railway, entering Croydon, where it falls into the Wandle. Along the 

 course of the Bourne, and especially near its source in Marden Park, the 

 land becomes saturated from overcharged springs, which ultimately form a 

 river of clear water, passing Caterham Junction in a channel about 4 feet 

 wide, and with a rapid current. That this stream is the accumulation of 

 water from springs, and not surface drainage, is I think evident, because it 

 is not turbid, as water from surface drainage usually is in this part of the 

 country after heavy floods. It is supposed to be the discharge of a subter- 

 ranean reservoir, which having been filled to a certain height, the waters 

 are drawn ofE as by a siphon. I apprehend the sources of the 

 Wandle are the overflowing of springs from the chalk district, rising out 

 of the gravels which overlie the chalk in the neighbourhood of Croydon 

 and Beddington, but not intermittent, as in the case of the Bourne. The 

 Wandle river abounds with remarkably fine trout, and but few 

 other kinds of fish are found therein. As the river approaches its 

 termination in the Thames it becomes afiected with the tidal water 

 and is contaminated with sewage, and loses its transparency and general 

 character, so that persons who know it only at Wandsworth would not 

 recog'nise it as the same stream running through Carshalton or 

 Beddington. The river and ponds connected with it rarely freeze. 

 (2.) A small stream rises near Maiden, and falls into the Thames at 

 Barnes. I know but little of this stream, and therefore cannot say much 

 about it. It has nothing like the volume of water that the Wandle has, 

 and, so far as I have been able to observe, it has not the brilliancy of that 

 stream, (3.) Still travelling west, the next river is the Hog's Mill River, 

 which has its principal source in abundant springs at Ewell. This river 

 is of similar character to the Wandle, rapid, clear, and abounding with 

 trout. It falls into the Thames at Kingston. (4.) The next river we have 

 is the Mole. This is altogether of a different character to the others. It 

 has its principal sources from the Wealden series, and to a large extent 

 derives its paters from the drainage of the country. It is true that one 

 considerable feeder has its sources in the Holmesdale Valley, one 

 branch rising in the valley between Bletchingley and White Hill, but 

 receiving its chief supply from the greensand, not from the chalk. Another 

 feeder comes from Merstham, and this supply appears to arise more from 

 the upper greensand than from the chalk. This is met again by a feeder 

 from Gatton Park, also arising outof the upper greensand. This Holmesdale 

 branch of the stream finds its way through a narrow valley in the lower green- 

 sand range at Eedhill, where that formation is cut down to the level of the 



