It seems likely that some vapours are capable of receiving shadows. When I have been bathing in a river with a muddy bottom, I have often seen my shadow on the cloud of muddy particles which I have disturbed from the bottom, in a manner something similar to that in which I should think this may occasionally take place. There is, however, another theory of it. When rays pass from a thin medium into a denser medium, the whole do not go through, but they are _strained_, as it were, and a part are kept back and reflected. It is thus that you see a reflection on a transparent pane of glass. If you breathe very lightly upon it, the reflection will be still more distinct, and the resemblance to the phenomenon we are describing probably greater. There are then two causes of reflection, the change of refracting power, and the presence of the watery particles. Something of this kind perhaps occurs on the top of the Brocken. A rush of cold air may set up from deep ravines, with water and marshy land at the bottom, on the West side, while the rising sun is genially warming the air on the east side of the mountains. Mind, I do not say that it is so, but it does not seem unlikely that two currents, one of cold air and the other of hot, thus ascend close to each other; and according to what I have told you, there would be a reflecting power in the plane of contact, which might be increased by the watery particles carried upwards. A kind of aerial screen would thus be formed, which might catch the shadow of a person on the opposite summit, cast upon it by the horizontal rays of the morning sun. Thus you may account for the image, and its being so greatly magnified, requires no further explanation than I have given above; as it only needs the supposition of a mass of heated air, with two colder ones on each side, being between the persons and the reflecting substance. The doubling of one of the figures was possibly occasioned by a reflecting surface having been formed on a different plane from the first, which might very easily occur. CONCLUSION. OF SOME OTHER WONDERS, AND HOW WE OUGHT TO USE OUR KNOWLEDGE OF THE WONDERS OF NATURE. I. I have now given you, my little friends an account of a few of the wonders of the wonderful world we live in, and I hope they have entertained you. I should like to have spoken to you of a great many other things, but it would make my book too large.