he pipes probably
occurred at the crossing of the puddle trench. A fissure in the puddle
was created, affording a creep for the water, which, once set up, would
rapidly increase the breach by scour; and this event was favored by the
manner in which the bank had been constructed and the unsuitability of
the material used, which, in the words of one engineer, had more the
appearance of a quarry tip than of a bank intended to store water. This
opinion of the cause of failure was, however, not adopted universally by
engineers, the line of pipes when examined being found to be, although
disjointed, fairly in line; and there having occurred a land slip in the
immediate neighborhood, it was suggested that the rupture might be caused
by a slip also having taken place here, especially as the substratum was
of flagstone rock tilted at a considerable angle. The formation was
millstone grit. This catastrophe induced an examination to be made of
other storage reservoir dams in the same district, and a report on the
subject was presented to Parliament by Sir Robert Rawlinson.

[Illustration: TYPICAL MASONRY AND EARTHWORK DAMS OF THE WORLD.]

The dam of Stubden reservoir, of the Bradford water supply, also on the
millstone grit, was constructed about 1859, and caused considerable
anxiety for a length of time, as leakage occurred in the culvert carrying
the pipes, under the embankment at a point a short distance on the down
stream side of the puddle trench. This was repaired to some extent by
lining with cast iron plates; and an entirely independent outlet was made
by driving a curved tunnel into the hill side clear of the ends of the
dam and lining it with cast iron plates. In this tunnel was then laid the
main of 2 ft. diameter, and as the original culvert again became leaky,
the water had to be lowered, the old masonry pulled out, and the space
filled in with puddle.

The Leeming compensation reservoir of the same water supply, with a dam
of 50 ft. in height, and culvert outlet, had to be treated somewhat in
the same manner, as, although the reservoir had never been filled with
water, in 1875, when it was examined previous to filling, it was found
that the culvert was cracked in all directions; and it was deemed best to
fill it up with Portland cement concrete, and drive a tunnel outlet
through the hill side, as described in the case of the Stubden reservoir.
The Leeshaw dam, which was being constructed at that time upon the same