On the Construction of' Meteorological Instruments. 241 



fixed on the axle of this cylinder. 

 b, Seven levers moving on a common wire at c, each supported 



by a small spring d. 

 €, e, Small catches for retaining the instruments in an upright 



or inclined position. 



f, A wire, represented by a dotted line to g, which keeps the 

 valve h, fig. 1.^ shut when the instrument is vertical, and al- 

 lows it to open when the instrument is moving to a horizontal 

 position. There is one such wire for each instrument. 



h, The vapour chamber, which is an oblong tin-box, connected 

 in front with the lamp d, fig. 1., and at the other extremity 

 with a narrow bent tube m, which terminates in the chimney 

 e, fig. 1. The vapour chamber is at some distance from the 

 wooden frame, and the space between them is filled with cot- 

 ton or powdered charcoal. 

 - n, n, Are thin metallic tubes which project into the vapour 

 chamber, and are shut at their under extremities. 



p, p, p, Are small bent levers, which, by means of short springs, 

 elevate the valves b, b, when these are freed by the wires j[/! 



Fig. 3. Represents a section of a small apparatus which may be 

 carried in the pocket. 



a, The frame or case. 



b, Two slips of metal bearing each a thermometer and atmi- 

 zomic-hygrometer, with a separate scale for each. 



c, A lever kept in its place by the spring d, and retaining b in 

 a vertical position by means of a catch. 



e, A revolving cylinder, with two projecting pins for depressing 

 the levers. When the ajjparatus is used, the cylinder is put 

 in motion by means of a pocket time-piece. 



/, The vapour chamber. 



g, A glass- vessel containing rain or distilled \\^ater, and which 

 may be raised or lowered on the upright stem h, 



i, A small glass-tube, having attached to its under extremity a 

 soft hair pencil, through which the water, in the glass- vessel, 

 slowly distils, so as to keep the bulbs of the atmizomic hy- 

 grometers constantly moist. There may be a separate tube 

 for each instrument, or one tube may terminate in two or 

 more branches, each mounted with its brush. The tube slides 

 up or down through a cork in the glass-vessel, so as to regu- 

 late or stop the flow of water. 



JULY OCTOBER 1826. Q 



