The great labour and expense bestowed on some kinds of staircases is well exemplified by Evelyn in his tour of France, who describes going to Blois, in 1664, and seeing there a palace built by Francis the First, the staircase of which, consisting of 274 steps, is mentioned by Palladio; he notices it as a wonderful piece of work, from its construction having occupied 1800 workmen during twelve years. “The stayre-case (he says) is devised with four entries or ascents, which cross one another, so that though four persons meet, they never come in sight, but by small loopholes, till they land.”--Memoirs of John Evelyn, 2nd edit. 4to. vol. i. page 59. 49. A portable Engine, in way of a Tobacco-tongs, whereby a man may get over a wall, or get up again being come down, finding the coast proving[2] [3] unsecure unto him. Footnotes [2] proveth insecure for him. P. [3] proveth. [_A Tobacco-tongs Engine._] The designation here given, when published in 1663, was doubtless generally understood, but the smallness of the “engine,” its very nature, and not less, its long discontinuance of use, now renders the passage obscure. It so happens, however, that a scientific experiment, in which this humble instrument was employed by the Honourable Robert Boyle, has preserved, for our information in this matter, the true figure of the “tobacco-tongs.” In the 3rd Volume of Boyle’s Works, folio, published in 1744, is recorded his pneumatical experiments on the falling of bodies in vacuo. Treating of “New experiments physico-mechanical, touching the spring of the air,” illustrated by the well-known experiment of dropping at the same time a guinea and a feather within an exhausted glass receiver, he says: “We so fastened a small pair of _tobacco-tongs_ to the inside of the receiver’s brass cover, that by moving a turning key, we might by a string tied to one part of them open the tongs, which else their own spring would keep shut.” [Illustration: Tobacco-tongs] In an illustrative engraved plate, accompanying his description, the fourth figure therein is designed to show the “tobacco-tongs,” which appear in the form of a figure of 8, as in the annexed diagram, where _a_, is the top or hand portion, being the largest oval, while the lower oval _b_, is not above one third its size, at which point this steel spring instrument was cut through, to form the tong or nippers. We imagine that a side view would be like the dotted figure _c_, _d_, where _d_, shows how the ends of these nippers were probably elongated a little, the more readily to take up and part with the tobacco or other material. The least pressure on the outside of the large oval, will extend the nippers _b_, _d_, which again close when such pressure is removed.