=148. Glaisher's Thermometer Stand.=--The thermometer stand consists of a horizontal board as a base, of a vertical board projecting upwards from one edge of the horizontal one, and of two parallel inclined boards, separated from each other by blocks of three inches in thickness, connected at the top with the vertical, and at the bottom with the horizontal board, and the air passes freely about and between them all. To the top of the inclined boards is connected a small projecting roof to prevent the rain falling on the bulbs of the instrument, which are carried on the face of the vertical board, with their bulbs projecting below it, so that the air plays freely on the bulbs from all sides. The whole frame revolves on an upright post firmly fixed to the ground, as shown in the engraving, fig. 94; and in use, the inclined side is always turned towards the sun. =149. Thermometer Screen, for use at Sea.=--This screen, or shade, was designed by Admiral FitzRoy, and has been in use for several years on board H.M. vessels and many merchant-ships. It is about twenty-four inches long by twelve wide and eight deep; having lattice-work sides, door, and bottom; with perforation also at top, so contrived that the air has free access to the interior, while the direct rays of the sun, rain, and sea spray are effectually excluded from the thermometers mounted inside. There is ample space for two thermometers placed side by side on brackets, at least three inches from each other or any part of the exterior of the screen. One thermometer should be fitted up as a "wet bulb" (see p. 105). A small vessel of water can easily be fixed inside the screen so as to retain its position and contents under the usual motions of the ship; and by means of a piece of cotton-wick, or muslin rag tied round the bulb of the thermometer and trailing into the cup of water, keep the bulb constantly moist. Self-registering thermometers should be protected by a similar screen. It has been found that thermometric observations made at sea are not valuable for scientific purposes unless the instruments have been duly protected by such a screen. =150. Anemoscope=, or Portable Wind Vane for travellers, with compass, bar needle, &c., shows the direct course of the wind to half a point of the compass. [Illustration: Fig. 95.]