. Transactions of the Royal Society of Edinburgh . assingover the wheel/, whose axle rests on friction-rollers at g and h; i is a spiral, which has acord wrapped onit carrying a weight Jc, whichbalances the vessel e; I is a dial, graduatedon the face near the circumference ; m an in-dex, attached to the common axle of thewheel and spiral; n a loose index under theindex m, which the latter carries forward bymeans of a projecting pin near the extre-mity ; o a tube passing under the cistern a,which, entering the bottom, proceeds upwardswithin the vessel e till its open extremity isabove the level
. Transactions of the Royal Society of Edinburgh . assingover the wheel/, whose axle rests on friction-rollers at g and h; i is a spiral, which has acord wrapped onit carrying a weight Jc, whichbalances the vessel e; I is a dial, graduatedon the face near the circumference ; m an in-dex, attached to the common axle of thewheel and spiral; n a loose index under theindex m, which the latter carries forward bymeans of a projecting pin near the extre-mity ; o a tube passing under the cistern a,which, entering the bottom, proceeds upwardswithin the vessel e till its open extremity isabove the level of the water in a neck of thevessel e; the other end of the tube o is sixfeet above the outer wall of the Observatory,where it is capped by a vane p ; at the topof the tube o three brass rods are joined,which carry a small tube in which a pin withinthe top piece q rests or turns ; the tube o isdouble at the top, containing between thetubes a quantity of mercury to the level r,the continuation of the cylindrical body ofMAG. AND MET. OBS., 1844. q. lxii Introduction to the Makerstoun Observations, 1844. the vane enters the mercury, and a double portion s acts as an outer cover to the mer-cury cistern; t is an aperture, 2 inches square. When the wind blows, this aperture ispresented to it, the wind then presses on the column of air within the tube o (beingprevented from escaping under the vane by the mercury), and ultimately on the topsurface of the vessel <?, forcing the latter up, turning the axle carrying the index m,which carries before it the index n, leaving it at its farthest excursion. The dial isgraduated as follows :—The surface of the top of the vessel e on which the windpresses is 78 square inches, therefore a pressure of 1 lb. on this surface is equivalentto ^ lb. on a square foot. Different weights are suspended on the wheel/, actingoppositely to the vessel e, and the position of the index for each weight shews thepressure on a square foot of surface equal to t
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Keywords: ., bookauthorroyalsoc, bookcentury1800, bookdecade1840, bookyear1848
