如果在晴朗的夏日仰望天空，我们会发现头顶上空的蓝色最为纯净、浓郁，而当我们背对太阳向高处看时也是如此。
If we look at the sky on a perfectly fine summer's day we shall find that the blue colour is the most pure and intense overhead, and when looking high up in a direction opposite to the sun.
Near the horizon it is always less bright, while in the region immediately around the sun it is more or less yellow.
The reason of this is that near the horizon we look through a very great thickness of the lower atmosphere, which is full of the larger dust particles reflecting white light, and this dilutes the pure blue of the higher atmosphere seen beyond.
And in the vicinity of the sun a good deal of the blue light is reflected back into space by the finer dust, thus giving a yellowish tinge to that which reaches us reflected chiefly from the coarse dust of the lower atmosphere.
在地平线附近，光线总是没那么亮，而在太阳周围的区域，光线或多或少呈黄色。
If we look at the sky on a perfectly fine summer's day we shall find that the blue colour is the most pure and intense overhead, and when looking high up in a direction opposite to the sun.
Near the horizon it is always less bright, while in the region immediately around the sun it is more or less yellow.
The reason of this is that near the horizon we look through a very great thickness of the lower atmosphere, which is full of the larger dust particles reflecting white light, and this dilutes the pure blue of the higher atmosphere seen beyond.
And in the vicinity of the sun a good deal of the blue light is reflected back into space by the finer dust, thus giving a yellowish tinge to that which reaches us reflected chiefly from the coarse dust of the lower atmosphere.
这是因为在地平线附近，我们的视线穿过了非常厚的大气层底层，那里充满了反射白光的较大尘埃颗粒，这冲淡了远处高层大气纯净的蓝色。
If we look at the sky on a perfectly fine summer's day we shall find that the blue colour is the most pure and intense overhead, and when looking high up in a direction opposite to the sun.
Near the horizon it is always less bright, while in the region immediately around the sun it is more or less yellow.
The reason of this is that near the horizon we look through a very great thickness of the lower atmosphere, which is full of the larger dust particles reflecting white light, and this dilutes the pure blue of the higher atmosphere seen beyond.
And in the vicinity of the sun a good deal of the blue light is reflected back into space by the finer dust, thus giving a yellowish tinge to that which reaches us reflected chiefly from the coarse dust of the lower atmosphere.
而在太阳附近，大量的蓝光被细小的尘埃反射回太空，因此到达我们的光线主要由低层大气中较粗尘埃反射而来，呈现出微黄色。
If we look at the sky on a perfectly fine summer's day we shall find that the blue colour is the most pure and intense overhead, and when looking high up in a direction opposite to the sun.
Near the horizon it is always less bright, while in the region immediately around the sun it is more or less yellow.
The reason of this is that near the horizon we look through a very great thickness of the lower atmosphere, which is full of the larger dust particles reflecting white light, and this dilutes the pure blue of the higher atmosphere seen beyond.
And in the vicinity of the sun a good deal of the blue light is reflected back into space by the finer dust, thus giving a yellowish tinge to that which reaches us reflected chiefly from the coarse dust of the lower atmosphere.
而在日落和日出时，这种效果会大大增强，因为光线到达我们这里所穿过的空气层非常厚。……
At sunset and sunrise, however, this last effect is greatly intensified, owing to the great thickness of the strata of air through which the light reaches us.
The enormous amount of this dust is well shown by the fact that then only we can look full at the sun, even when the whole sky is free from clouds and there is no apparent mist.
But the sun's rays then reach us after having passed, first, though an enormous thickness of the higher strata of the air, the minute dust of which reflects most of the blue rays away from us, leaving the complementary yellow light to pass on.
Then, the somewhat coarser dust reflects the green rays, leaving a more orange-coloured light to pass on; and finally some of the yellow is reflected, leaving almost pure red.
随着太阳高度的每一次变化，景象也随之改变；尤其是当太阳沉入地平线以下时，由于更有利的角度，大量的彩色光线反射向我们。……
But owing to the constant presence of air currents, arranging both the dust and vapour in strata of varying extent and density, and of high or low clouds which both absorb and reflect the light in varying degrees, we see produced all those wondrous combinations of tints and those gorgeous ever-changing colours which are a constant source of admiration and delight to all who have the advantage of an uninterrupted view to the west and who are accustomed to watch for those not infrequent exhibitions of nature's kaleidoscopic colour painting.
所有这一切无与伦比的辉煌都归功于——尘埃！
With every change in the altitude of the sun the display changes its character; and most of all when it has sunk below the horizon, and owing to the more favourable angles a larger quantity of the coloured light is reflected toward us.
Especially when there is a certain amount of cloud is this the case.
These, so long as the sun was above the horizon, intercepted much of the light and colour; but when the great luminary has passed away from our direct vision, his light shines more directly on the under sides of all the clouds and air strata of different densities; a new and more brilliant light flushes the western sky, and a display of gorgeous ever-changing tints occurs which are at once the delight of the beholder and the despair of the artist.