Bold Composure Sectory 13
Page 01

Crossing the solar spectrum are hundreds and hundreds of dark lines. These could not at first be explained, because this fact of discriminative absorption was not known. We understand now. The sun's white light comes from the photosphere, but between us and the photosphere there is, as we have seen, another solar envelope of relatively cooler vapours--the reversing layer. Each constituent element in this outer envelope stops its own kind of light, that is, the kind of light made by incandescent atoms of the same element in the photosphere. The "stoppages" register themselves in the solar spectrum as dark lines placed exactly where the corresponding bright lines would have been. The explanation once attained, dark lines became as significant as bright lines. The secret of the sun's composition was out. We have found practically every element in the sun that we know to be in the earth. We have identified an element in the sun before we were able to isolate it on the earth. We have been able even to point to the coolest places on the sun, the centres of sun-spots, where alone the temperature seems to have fallen sufficiently low to allow chemical compounds to form.

Every one has seen a cornfield. If you pluck up one of the innumerable wheat plants which are fixed in the soil of the field, about harvest time, you will find that it consists of a stem which ends in a root at one end and an ear at the other, and that blades or leaves are attached to the sides of the stem. The ear contains a multitude of oval grains which are the seeds of the wheat plant. You know that when these seeds are cleared from the husk or bran in which they are enveloped, they are ground into fine powder in mills, and that this powder is the flour of which bread is made. If a handful of flour mixed with a little cold water is tied up in a coarse cloth bag, and the bag is then put into a large vessel of water and well kneaded with the hands, it will become pasty, while the water will become white. If this water is poured away into another vessel, and the kneading process continued with some fresh water, the same thing will happen. But if the operation is repeated the paste will become more and more sticky, while the water will be rendered less and less white, and at last will remain colorless. The sticky substance which is thus obtained by itself is called gluten; in commerce it is the substance known as maccaroni.

Sometimes, however, geology does not, on the face of it, come into the reckoning. Thus I might have asked the reader to assist at the digging out of a cave, say, one of the famous caves at Mentone, on the Italian Riviera, just beyond the south-eastern corner of France. These caves were inhabited by man during an immense stretch of time, and, as you dig down, you light upon one layer after another of his leavings. But note in such a case as this how easily you may be baffled by some one having upset the heap of clothes, or, in a word, by rearrangement. Thus the man whose leavings ought to form the layer half-way up may have seen fit to dig a deep hole in the cave-floor in order to bury a deceased friend, and with him, let us suppose, to bury also an assortment of articles likely to be useful in the life beyond the grave. Consequently an implement of one age will be found lying cheek by jowl with the implement of a much earlier age, or even, it may be, some feet below it. Thereupon the pre-historian must fall back on the general run, or type, in assigning the different implements each to its own stratum. Luckily, in the old days fashions tended to be rigid; so that for the pre-historian two flints with slightly different chipping may stand for separate ages of culture as clearly as do a Greek vase and a German beer-mug for the student of more recent times.

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