"You will notice a very large number of peaks in this and the other neighbouring ranges—in fact, several thousands have been marked on our large maps.
"Cutting diagonally in a north-westerly direction, completely through the Alps, you will notice a long and deep valley. This is known as the 'Great Alpine Valley,' and is over eighty miles long, and varies from about three miles to six and a half miles in width. At the eastern end it is some 11,000 feet deep, debouching on to the plain in several comparatively narrow passes, whilst at its north-western extremity it is very shallow, and emerges on to what is known as the Sea of Cold, which covers an area of about 100,000 square miles. This valley seems to afford another example of formation by the action of water.
"Amongst the three thousand peaks comprised in the Apennine range just below the Alps, are several mountains of considerable altitude," I remarked, pointing out Mount Huygens, nearly 20,000 feet high, Mount Hadley, 15,000 feet, and Mount Woolf, 12,000 feet in height. "This range curves round towards the east, and finishes with a fine ring-plain called Eratosthenes—some thirty-seven miles in diameter, with a floor depressed 8000 feet below the lunar surface. It encloses a central mountain, and on the east wall there is one peak which rises 16,000 feet above the floor.
"The ranges in this part of the moon are, perhaps, more like those on our earth than others to be found on its surface, but much more wild and rugged.
"Eastward and northward of these ranges is the Sea of Showers, on which there are several fine ring-mountains and walled plains—notably Autolychus and Aristillus, two very perfect ring-mountains some 9000 feet high.
"One of the most striking, on account of its size and situation, is that large one which is called Archimedes, and is about fifty miles in diameter; and you will notice that a rugged mass of mountains and high hills extends from it to a distance of over a hundred miles on the south. The floor of this walled plain is only about 600 feet below the general level, and the mountain walls average about 4000 feet in height; but there is at least one peak some 7000 feet high.
"You will see a little below and westward of Archimedes the commencement of a system of large cracks or crevasses in the lunar surface which are known as 'rills.' Many such systems are found in various parts of the moon; some of the cracks are comparatively shallow, but, according to Professor Langley, others are known to be at least eight miles deep, and may be infinitely deeper, though I cannot say I understand how these great depths have been arrived at. The length of the cracks varies from a few miles to over three hundred miles, and from a few hundred yards to some miles in width. They are attributed partly to volcanic action, but mainly to the contraction of the crust of the lunar globe as it became cold. Being so much smaller, the moon would cool much more rapidly than the earth, and the disruptive effects would necessarily be greater."
John here touched my arm, and pointing to some mountains on the borders of a large elongated oval area, close to the north-western terminator where the sun was setting, asked me what they were. I explained that the dark area was known as the Mare Crisium, or Sea of Conflicts, and is possibly the deepest of the large lunar depressions.
"It is about 280 miles long from north to south, and 355 miles wide from east to west, but, owing to its position, the width is seen from the earth very much foreshortened, so that it really looks nearly twice as long as it is wide. It contains an area of about 75,000 square miles, thus being as large as the combined area of Scotland and Ireland, and the five largest northern counties of England. It is surrounded by mountains, some being over 11,000 feet high, reckoning from the dark floor."
I drew their attention to Proclus—a ring-mountain on the eastern side of this sea—which is about eighteen miles in diameter, and the second brightest of the lunar formations. "From its neighbourhood several bright streaks diverge in different directions, two extending a long way across the dark area, and there is a longer one striking towards the north and another towards the south at an angle of about 120 degrees with each other.