The spider lines are strained across the best instruments at Greenwich and elsewhere; and when the spinners of these beautifully fine threads disturbed the accuracy of the tube in the western wing of the old Observatory, it was said to be but fair retaliation for the robberies the industrious insects had endured. A narrow stair leads from the unused rooms of the old Observatory to its leaded roof, whence a magnificent view is obtained; the park, the hospital, the town of Greenwich, and the windings of the Thames, and, gazing further, London itself comes grandly into the prospect. The most inveterate astronomer could scarcely fail to turn for a moment from the wonders of the heavens to admire these glories of the earth. From the leads, two turrets are reached, where the first constantly active operations in this portion of the building, are in progress. At the present time, indeed, these turrets are the most useful portions of the old building. In one is placed the well-known contrivance for registering, hour after hour, and day after day, the force and direction of the wind. To keep such a watch by human vigilance, and to make such a register by human labour, would be a tedious, expensive, and irksome task; and human ingenuity taxed itself to make a machine for perfecting such work. The wind turns a weather-cock, and, by aid of cog-wheels the motion is transferred to a lead pencil fixed over a sheet of paper, and thus the wind is made to write down the direction which itself is blowing. Not far distant is a piece of metal, the flat side of which is ever turned by the weather-cock to meet the full force of the wind, which, blowing upon it, drives it back against a spring. To this spring is affixed a chain passing over pullies towards another pencil, fixed above a sheet of paper, and moving faithfully, more or less, as the wind blows harder or softer. And thus the ‘gentle zephyr’ and the fresh breeze, and the heavy gale, and, when it comes, the furious hurricane, are made to note down their character and force. The sheets of paper on which the uncertain element, the wind, is bearing witness against itself, is fixed upon a frame moved by clockwork. Steady as the progress of time, this ingenious mechanism draws the paper under the suspended pencils. Thus each minute and each hour has its written record, without human help or inspection. Once a day only, an assistant comes to put a new blank sheet in the place of that which has been covered by the moving pencils, and the latter is taken away to be bound up in a volume. The book might with truth be lettered ‘The History of the Wind; written by Itself,’—an Æolian autobiography. Close by is another contrivance for registering in decimals of an inch the quantity of rain that falls. The drops are caught, and passing down a tube, a permanent mark is made by which the quantity is determined.