19 LETTER III. BLESS THE LORD, O MY SOUL. O LORD MY GOD, THOU ART VERY GREAT; THOU ART CLOTHED WITH HONOR AND MAJESTY. WHO WHO COVEREST THYSELF WITH LIGHT AS WITH A GARMENT: STRETCHEST OUT THE HEAVENS LIKE A CURTAIN: WHO LAYETH THE BEAMS OF HIS CHAMBERS IN THE WATERS; WHO MAKETH THE CLOUDS HIS CHARIOT: WHO WALKETH UPON THE WINGS OF THE WIND.-Psalm civ. 1-3. My dear children, In all the days of Creation, as I before remarked, there was a wonderful provision made for those which followed. This is especially the case in the second day, when the Firmament, or what is better known to us as "the Atmosphere," came into existence. The language which records its Creation is very full:"And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was And God called the firmament Heaven. And the evening 80. and the morning were the second day." Thus did the Lord by this one act of Creative Power bring into being that by which all life, whether vegetable or animal, was destined to be sustained. A vast body of water was also gathered up into the atmosphere, and suspended there in clouds, which became as the garment thereof (Job xxxviii. 9); thus the waters were divided from the waters, and the means provided by which the earth might be continually refreshed by the early and the latter rain; for the clouds became from this day God's appointed reservoir of the rain and snows, which in due season should come and water the earth, to make it bring forth and bud, giving seed to the sower and bread to the eater (Isa. lv.). But the subject of the atmosphere is so full of interest, both in its formation and various properties, that we must not hastily pass away from it; and therefore I will endeavour to inform your young minds as to these two particulars. And here I must of necessity use some scientific terms; but though I know such hard names at first sight seem difficult to remember, yet it is manifest, that the language of science, if not the most beautiful is the most expressive; for every word carries within itself its own signification; whilst, therefore, dear children, I will seek to avoid an unnecessary use of these terms, I have little doubt but we shall soon agree that they are even easier to retain than words in common use. First, then, let me explain to you the formation of the atmosphere, or the air, with which we are surrounded. Naturalists that is, men of science who have made these subjects their especial study-have ascertained that the air is composed of two principal gases, or elastic fluids, which have been named by them, Oxygen and Nitrogen. The property of the first is vitalit is replete with life: the second has no power of life, and so has been called azote, that is, without life: but as the oxygen would be too strong alone, the nitrogen dilutes it, as water dilutes wine. The relative proportions are,- twenty parts oxygen, eighty nitrogen. In addition to these, there is a small proportion of carbonic acid gas, also hydrogen, but only in the proportion of one part to ninety-nine. Relative to the height of the atmosphere, it is calculated that it does not extend above fifty miles,* expanding all the while as it ascends; and at that * It is a singular thing to say, that we can weigh that which we cannot see; and yet this is strictly true of the atmosphere; and we little think how it is pressing upon us on every side; for it is calculated, that on the body of a full grown man, its pressure is equal to 30,000 pounds; but then, as it presses equally on every side, and as also we have a resistance within, we not only do not feel any inconvenience from it, but positive blessing: but as a proof of the pressure of the atmosphere, supposing you doubled or trebled the weight of the atmosphere, that is, condensed two or three atmospheres into one, around a thin glass vessel, from which you had exhausted the air, the outward pressure would crush it to pieces. But the principle of expansion of the atmosphere is greatly more wonderful than that of its condension; for it is calculated, that at the height of 500 miles, a cubic inch of rarified air would fill a sphere equal in diameter to the orbit of Saturn. The proof of the power of expansion is very simple.-Suppose you fill a bladder with atmospheric air, and divide it into 100 parts; and then exhaust height it becomes so rarified that it cannot sustain life: indeed, the Æronauts, or air sailors, as the word means, that have never ascended beyond 5 miles, have even then found great difficulty in breathing; and on account of the atmosphere being so much lighter, they have in many cases bled profusely from the nose and mouth;-but though the air thus expands, yet it never in the least degree varies its relative proportions. One traveller brought some down from Chimborasso, the highest of the Andes (that amazing range of mountains which I have so often described to you), and compared it with some taken from the lowest valley beneath; but the proportions were the same. Others again, have examined the pestilent marshes near Rome; but in this case also there was not the slightest variation. If death was there, it arose not from the absence of the vital oxygen (that was there true to its proportions), but from some principle of too subtle a nature to be detected by chemical analysis. Indeed, the infectious atmosphere of an hospital has been examined with great care, even when its ill odour was intolerable, but no discernible difference could be perceived. Having thus far explained the nature of our atmosphere, I will now endeavour to make plain to you its properties. ninety-nine parts, and put it into a vessel air tight; exhaust the air from the vessel, and the bladder would swell out quite distended: reverse the experiment, and let in the atmospheric air, and it would shrink up as if there was nothing in it. The first great property of the atmosphere, as I have before remarked, is to sustain animal and vegetable life. The absence of it to one or other would cause instant death. This has been abundantly proved by experiment: for place either an animal or vegetable in any vessel air tight, and then exhaust the air, and life is fled. But, not only would death instantly ensue, if the air were taken from us; but if it ever varied its proportions, all would be in misery and yet near 6000 years have run out since its formation; and the little child just born inhales it with the same freedom as the first offspring of man. But, let us suppose, for instance, that we inhaled nothing but the pure oxygen, or vital air; after a little, the lungs would become so excited, that nature could not long sustain the unnatural stifling fulness; and if, on the contrary, we inhaled only nitrogen, we should die; for it has been ascertained by experiment, that animals put into a vessel filled only with nitrogen, die instantly. And then, if the PROPORTIONS WERE DIFFERENT:-the oxygen prevailing, we should be in perpetual excitement, and rendered perfectly miserable; the nitrogen prevailing, we should be continually panting for breath, and at last faint away and die. But the air, measured and proportioned by the hand of infinite tenderness and compassion, the simple act of respiration, which the most of men enjoy, is in itself a continual pleasure; but this we seldom think about, until, from bodily infirmity, or being shut up in a little room with a great number of people, like the poor suf |