s are so narrow in these old towns is, that in
the ancient times, when they were laid out, there were no wheeled
carriages in use, and the streets were only intended for foot
passengers. When, at length, carriages came into use, the houses were
all built, and so the streets could not easily be widened.

Our travellers at length reached a large, open square, on the farther
side of which the immense mass of the cathedral was seen rising, like a
gray and venerable ruin. The wall which formed the front of it, and
which terminated above in the unfinished mason work of the towers, was
very irregular in its outline on the top, having remained just as it was
left when the builders stopped their work upon it, five hundred years
ago. The whole front of this wall, having been formed apparently of
clusters of Gothic columns, which had become darkened, and corroded, and
moss-covered by time, appeared very much, as Rollo had said, like a
range of cliffs--the resemblance being greatly increased by the green
fringe of foliage with which the irregular outline of the top was
adorned. It may seem strange that such a vegetation as this could arise
and be sustained at such a vast elevation. But ancient ruins are almost
always found to be thus covered with plants which grow upon them, even
at a very great height above the ground, with a luxuriance which is
very surprising to those who witness this phenomenon for the first time.
The process is this: Mosses and lichens begin to grow first on the
stones and in the mortar. The roots of these plants strike in, and
assisted by the sun and rain, they gradually disintegrate a portion of
the masonry, which, in process of time, forms a soil sufficient for the
seeds of other plants, brought by the wind, or dropped by birds, to take
root in. At first these plants do not always come to maturity; but when
they die and decay, they help to increase the soil, and to make a better
bed for the seeds that are to come afterwards. Thus, in the course of
centuries, the upper surfaces of old walls and towers become quite
fertile in grass and weeds, and sometimes in shrubbery. I once gathered
sprigs from quite a large rosebush which I found growing several hundred
feet above the ground, on one of the towers of the cathedral of
Strasbourg. It was as flourishing a rosebush as I should wish to see in
any gentleman's garden.

What Rollo meant by the bears and wolves which he said he saw looking
down from these cliff-li