XIII. 



ADDRESS. 



GEOLOGICAL AND OTHER WORK IN HERTFORDSHIRE. 



By the President, William AViriTAKEii, B.A., r.R.S.,^^<'itCor»;i>\ 

 V (J O 3 2- Fres. G.S., Assoc. Inst. C.E. /^* Zooio«v ^*' 



Deliveird at the Anniversary Meeting, 2Sth February, 1899.1 »^UL 20 1^42 



Ladies axd Gentlemex, — ^' ^*'" 



Before takiug up the subject of my Address, I may add a note 

 to that of lust year, which was unfortunately too late for insertion 

 as a postscript. The subject has been treated in some detail by 

 Mr. Hopkinson, but my note may be acceptable as a supplement. 



The unexpected has certainly an uncomfortable habit of 

 happening:, and I must own to feeling some surprise on hearing, 

 in September, that the Chadwell Spring had entirely failed as 

 a source of supply by overflow. Water was, however, pumped up 

 from it later on. 



I took the first chance of visiting the place, and was there on 

 the 24th of September, with Mr. Hopkinson, being joined after- 

 wards by Mr. Francis, Engineer to the New River Company. 



The water in the spring seems to have gradually sunk until it 

 got below the level of that in the New River. Consequently, 

 instead of the water from the spring flowing in its accustomed 

 course along a short conduit north-eastward to the New River, 

 a flow was set up in the reverse direction. 



Of course this was at once stopped by a temporary dam across 

 the conduit. The spring continued to get lower, and at our visit 

 its water was about 6|- feet below that in the conduit. It must be 

 noted, however, that the conduit is an artificial stream, and that 

 its water-level is above that of the natural river. 



Things have been so artificialized in this neighbourhood, how- 

 ever, that such a thing as a natural stream cannot be found. So 

 far as I could tell, the nearest approach to this, the Manifold Ditch 

 (where it exists), has its water some 3 feet lower than that of the 

 New River. We are therefore faced with the fact that Chadwell 

 Spring was some 3 feet or more below the level of the natural Lea. 



The spring was not dry ; for we saw a diver go down into it ; 

 but all the bottom part that was bare was thickly coated with mud, 

 Avhich also appeared along the southern border, and I cannot but 

 think that this deposit has not, at all events, improved the flow 

 fi'om the spiing, or rather set of springs. 



VOL. X. — PART IV. 9 



