ST. ALBANS AND ITS NEIGHBOURHOOD. 
219 
into the Middle Chalk through the Upper Chalk which flanks 
the valley on either side, from its source to a quarter of a mile 
above Harpenden Bury, which is about a mile above the bridge 
at Redbourn. It follows that at this point the Chalk Rock 
occurs. In normal conditions of rainfall the river in autumn 
usually has its source here in springs, sometimes being augmented 
by springs a little lower down, but more often they are dry. 
For a short distance the water is held in its channel by the 
alluvium which the river has deposited, but at Harpenden Bury 
it decreases in volume, showing that it is no longer so upheld, 
and in an orchard a little below the farm it finally disappears 
down a swallow-hole, the river-channel continuing dry for three- 
quarters of a mile. Within a quarter of a mile north of the 
bridge at Redbourn there are several springs in action in the 
river-bed, and there are others at Church End, nearly half 
a mile west of the river, supplying ponds from which water 
flows into the Yer, this little stream now being its only tributary. 
In the spring of 1904, after a year of excessive rainfall, the 
river rose above Markyate Street, four miles at least higher up 
its valley than usual, and at 100 feet higher level. Then there 
was a stream flowing for nearly a mile into the ponds at Church 
End, Redbourn. This is the old Womer Brook, the flowing of 
which in ancient times was believed to presage some calamity. 
It is said that the water had a slightly red colour, hence the 
name of the village and the origin of the superstition. 
Matthew Paris ( cir. 1250) says that “the Werlam river,” as 
he calls it, “ was once very large, and flowed about the city.” 
The Colne has had a much more chequered career than the 
Yer. At one time it was doubtless much the larger river at its 
confluence with the Yer ; now it is much the smaller. It usually 
rises in the vicinity of Colney Heath ; in a dry season it has had 
its source a little above London Colney; and after a very wet 
period about ten miles higher up its valley, a mile west of 
Barnet. A stream rises there still, flowing north for a few 
miles over London Clay, but when it passes over the Reading 
Beds and arrives at the Chalk, it begins to sink into swallow- 
holes. This part of its course is called the Mimms Hall Brook. 
From Mimms Hall to Water End there are several swallow- 
holes in the bed of the brook, but the largest are in Potterells 
Park, just outside our area. Seldom does the water reach 
those, for any which escapes one higher up the stream is sure, 
except on very rare occasions, to be entrapped by another. The 
writer has, however, seen it rushing down the Potterells swallow- 
holes with a roar that was heard for a long distance, and on 
another occasion flowing continuously for the whole course of 
the river, converting the Water End corner of Potterells Park 
into a lake, and flooding the country about Colney Heath and 
Smallford. The Chalk was then saturated up to the surface in 
this district, and possibly the swallow-holes were converted into 
springs. 
