Well, hot air, like hot water, is less dense than cold air; also water is more dense than air. You could not run along as quickly in the water as you could in the air; you could not strike a person with your hand under water hard enough to hurt him; and this is because the water is more dense or solid than air: therefore, air with a good deal of moisture in it is more dense than when dry. But along the hot sands of Pooree, close to the sea-shore, there must be a great deal of heat and also a great deal of moisture.
In the direction in which you look to see the mirage I mentioned, there is a small piece of stagnant water from which much moisture must arise under the burning heat of the sun; consequently there must be much refraction in all directions. And this is seen in looking the right way from all parts of the Pooree sands; and from the particular point to which I have alluded, this picture, owing, I suppose, to certain marks in the sand, assumes the appearance of a castle, houses, &c. All this is a very rough explanation; but it may serve to give you some idea of the probable cause of the mirage. Ships have sometimes appeared to be sailing in the air from the same cause; and distant coasts, which were far below the horizon, have been distinctly seen by means of the refraction.
Guzzeepuddee, 8 miles from Balasore, January 12.
Yesterday morning about four o'clock we started from Balasore on horseback. The party consisted of the magistrate, the surgeon, and myself. It was a brilliant moonlight, but somehow I thought I should like to finish my night's rest, and therefore soon got into my palanquin, and had a most comfortable nap. I was awakened at daybreak by my bearers stopping and telling me that they did not know the way to Guzzeepuddee. I got out of my palanquin, loaded my gun, inquired my way of the first native I saw, sent my palanquin on, and then with two servants entered the jungle. Whereabout the magistrate and the doctor were I had not the slightest idea. I had a delightful ramble through a jungle, many of the natives following me from each village through which I passed, and appearing to take great interest in the success of my sport.
I went on, with my broad-brimmer hat and brown leather gaiters, followed by twenty or thirty black fellows, forcing my way through the thickest, densest shrubberies, thinking at every instant that I might come suddenly on a large bear. Every now and then a break would occur in the jungle, and I would emerge from the tangled thicket into a broad open space of three or four acres, covered with the smoothest turf, interspersed here and there with the graceful bamboo, and surmounted on all sides with a literal wall of trees and underwood. On their branches sat the splendid wild fowls and the beautiful peacocks, whilst from all sides I heard the soft cooing of the doves.