Recently, much attention has been paid to the dust which is found on roofs and ledges at great heights. This meteoric dust, as it is called, consists of minute particles of iron, which are thought to fall from the highest part of the atmosphere, or possibly to be attracted to the earth from space. Lightning usually strikes the roof. The whole subject of lightning-conductors has been re-opened of late years, there being reason to think that mistakes have been made in the manner of their erection. The reason English roofs are high-pitched is not only because of the rain, that it may shoot off quickly, but on account of snow. Once now and then there comes a snow-year, and those who live in houses with flat surfaces anywhere on the roof soon discover how inconvenient they are. The snow is sure to find its way through, damaging ceilings, and doing other mischief. Sometimes, in fine summer weather, people remark how pleasant it would be if the roof were flat, so that it could be used as a terrace, as it is in warmer climates. But the fact is, the English roof, although now merely copied and repeated without a thought of the reason of its shape, grew up from experience of severe winters. Of old, great care and ingenuity--what we should now call artistic skill--were employed in contracting the roof. It was not only pleasant to the eye with its gables, but the woodwork was wonderfully well done. Such roofs may still be seen on ancient mansions, having endured for centuries. They are splendid pieces of workmanship, and seen from afar among foliage, are admired by every one who has the least taste. Draughtsmen and painters value them highly. No matter whether reproduced on a large canvas or in a little woodcut, their proportions please. The roof is much neglected in modern houses; it is either conventional, or it is full indeed of gables, but gables that do not agree, as it were, with each other--that are obviously put there on purpose to look artistic, and fail altogether. Now, the ancient roofs were true works of art, consistent, and yet each varied to its particular circumstances, and each impressed with the individuality of the place and of the designer. The finest old roofs were built of oak or chestnut; the beams are black with age, and, in that condition, oak is scarcely distinguishable from chestnut.