Ix PROCEEDINGS OF THE 



remained in portions of the meadow above the Harratt's End Lane, 

 but no current was observable beyond the meadow below. 



At its present source, Professor Attfield, who was one of the 

 party, took a sample of the water for analysis. He reports that it 

 was the ordinary chalk-water of the district, for it contained, per 

 gallon, 12 grains of chalk ; 4 grains of similar calcareous matter 

 formed of about equal parts of chlorides, nitrates, and sulphates ; 

 a little more than a grain of saline substances ; and the merest 

 traces of vegetable organic matter. While too hard for economical 

 or serviceable use with soap, it was, he says, of very good quality 

 for drinking purposes. 



From the lane just above this spot the course of the Bourne 

 was well seen, and here Mr. Evans explained the distinguishing 

 characteristics of the stream. The Bourne, he said, usually runs 

 about once in seven years, but recently it has flowed about once in 

 three years. Its flow is dependent not on the rainfall at the time, 

 but upon the rain which has fallen six, twelve, or even more 

 months previously. This is to a certain extent the case with every 

 stream flowing through a chalk country ; for the ground is so 

 porous that during the summer months it absorbs all the water 

 falling upon it, this being given out again by evaporation or 

 absorbed by vegetation. During the winter months usually 7 or 8 

 inches of the rain which falls on the surface descends through three 

 feet of soil, but during the summer there is scarcely any percolation 

 to that depth. The surface or gradient of the water in the chalk 

 forms an angle which is determined by the fi'iction of the rock and 

 the amount of the rainfall. In the Upper Chalk this angle is about 

 12 feet 6 inches to the mile, but in the Lower Chalk it is 19 or 20 

 feet to the mile. As the actual inclination of the valley of the 

 Bourne is about 20 feet to the mile, it is therefore necessary for a 

 sufficient quantity of rain to fall to cause the angle of the under- 

 ground reservoir to assume a higher inclination than this, in order 

 that the surface of this reservoir may appear above ground as the 

 Hertfordshire Bourne. 



A pleasant walk of about a mile and a half along a stretch of 

 Buckinghamshire lanes brought the party to a once-fortified en- 

 closure within which is a farm-house, at present known as Chesham 

 Grove. It is believed to have been a moated grange of consider- 

 able pretensions, and is probably of mediaeval date. Mr. Goodson, 

 the occupant of the farm, supplied the party with all the informa- 

 tion he possessed respecting his interesting residence, and kindly 

 opened a large barn for inspection. This was evidently a portion 

 of the old mansion, probably the dining-hall, several bricked -up 

 windows and doorways bearing unmistakable testimony to its 

 antiquity. Tradition reports that Protestant worship was per- 

 formed in this building during the reign of Queen Mary, when no 

 other room could be obtained in the neighbourhood. The octagonal 

 corner towers, the remains of the outer wall, and the deep fosse, 

 were inspected with much interest. The latter, which, completely 

 surrounds the enclosure, is still perfect. The bottom of the moat 



