“Mr Pentland, Sir—Take this bottle home and drink your own health. You can’t do less. It was distilled under your nose the first day you came to look for us, and bottled for you while you were speaking to the little boy that made a hare of you. Being distilled then under your nose, let it be drunk in the same place, and don’t forget while doing so to drink the health of
G. S.”
The incident went abroad like wildfire, and was known everywhere. Indeed for a long time it was the standing topic of the parish; and so sharply was it felt by Pentland that he could never keep his temper if asked, “Mr Pentland, when did you see little George Steen?”—a question to which he was never known to give a civil reply.
THE GLOBE OF THE EARTH.
We were surprised very much some time ago at considering how much of the surface of the globe is covered by the waters of the lakes and oceans, and took the opportunity then of adverting to the importance of water in the general economy of nature. When, however, we pass to the consideration of the magnitude of the earth itself, the relative proportion of water appears to be much less considerable.
Although there are many places in the great Atlantic and Pacific Oceans where the depth of water is very great, yet it has been deduced from principles that are not liable to much error, that the general or average depth does not exceed three miles. It may appear very strange that we can assert any thing positive about the depth of water in those seas, that are to the lines used for sounding quite unfathomable; but it is effected very simply. Every person has seen a wave advancing along the level surface of a canal, and by observing with a watch, it could easily be found to move more quickly at some times than at others. The deeper any part of the canal is, the more rapidly does the wave move along; and partly by experiment, and partly by reasoning, the connection between the depth of the water and velocity of the wave has been discovered. Now, the tide which comes to Dublin every twelve hours is produced by the influence of the sun and moon on the vast body of water in the Southern Pacific Ocean; and the great wave there formed turns round Cape Horn, and passes up the Atlantic Ocean, to arrive at the coasts of Europe and North America. The time occupied by this great wave in passing from one end to the other of the Atlantic can thus be known, and, precisely as in a canal, the depth of water thus calculated.
The circumference of the earth at its widest part is about 25,000, and its diameter 8000 miles. Hence the sheet of water which constitutes the ocean forms but 3-4000ths of its thickness, or nearly the same proportion as if we took an eighteen inch globe, and having spilled water on its surface, allowed all the excess of water to drain off. The remaining wetness would represent pretty nearly the condition of the waters of the ocean on the surface of the earth. By this means we can form, though obscurely, to our minds, an idea of the great magnitude of the earth itself. This magnitude renders also very inconsiderable those inequalities on the surface of the earth which constitute our highest ridges of mountains. A true model of Mont Blanc, the highest of European mountains, if constructed on the eighteen inch globe before referred to, would be unfelt by a finger drawn along its surface, and it would be only some of the highest peaks of the Andes and Himalayah that could be distinctly felt. Where man also employs his most gigantic energies and greatest efforts of skill to penetrate below the surface, forming mines by which the supplies of coal, of iron, of copper, and other minerals, have been obtained from the earliest times, the cavities that he makes can only be compared with the trace given by the point of a pin that had lightly touched the globe, and which would require a favourable incidence of light to see.
The earth is therefore almost perfectly a smooth and solid ball. It is, however, almost certain that it was not always solid. It is, on the contrary, almost certain that at a period far exceeding in remoteness any time of which mere human indications can be found, the globe of the earth was one mass of liquid matter, heated to a degree exceeding our most intense fires, and wherein were melted all together the various elements which have since arranged themselves into their present forms. From having been thus liquid, the earth, which, revolving on its axis, produces by the side it turns to the sun the alternating day and night, has bulged out where the rotation of the surface is most rapid, at the equator, and has become flattened at the extremities of its axis, at the poles, just as a thin hoop which we spin round becomes compressed. The amount of this flattening is however very small. The equatorial diameter of the earth being accurately 7925, and the polar diameter being 7898, the compression is 27 miles.
To account for the existence of this compression, the earth must have been originally liquid, for otherwise the rotation on its axis could not have generated this regular form. If it had been solid when it began to revolve, it should either have retained its original form, or it should have broken in pieces; but certainly unless it had been liquid, it could not have arrived at the exact degree of flattening which its velocity of rotation should have produced in a liquid mass.
The intensely heated and liquid earth, revolving in the cold and empty spaces of the planetary system, gradually must have lost its excess of heat. Cooling most rapidly at the surface, it there solidified, and generated the first rocks. The loss of heat still going on, the solidification proceeded to a greater and greater depth, and should ultimately have reduced the earth to the same temperature as the empty space among the stars. The temperature of space has been calculated to be almost the same as that in the winter at Melville Island, in northernmost America, that is, 56 deg. below zero, or as far below the freezing point of water as the temperature of the hottest water that the hand can bear is above it. The earth is, however, not allowed to cool to that degree. It receives from the sun by radiation a quantity of heat which counteracts its tendency to cool, and hence the mean temperature of the surface of the earth has remained the same from the earliest historical epochs. In fact, at the surface we can find no trace of that original and internal great heat, the temperature of the surface of the earth being regulated altogether by the effect of the sun’s rays; but if we dig down to a moderate depth, about 45 feet, the influence of the sun becomes insensible. Within that space also we can detect a very curious and important arrangement of the heat. It is not that the whole surface becomes warmed in summer and cold in winter, but the heat which is received from the sun in one summer travels by conduction beneath the surface, and is succeeded by the heat of the next summer, an intervening and cooler layer corresponding to the winter time, so that at a depth of 20 feet we may detect the heat which had fallen upon the surface four or five years before, this space of 45 feet being formed of numerous layers like the coatings of an onion, one for each year, until becoming less and less distinct, according as the depth increases, they join together in forming the layer of invariable temperature in which all the effect of the sun’s heat is lost.