45, COENHILL, B.C., AND 122, REGENT STREET, W., LONDON. 



135 



145. Our engraving (fig. 135) exhibits the 

 general internal arrangement of the Dial Barometer. 



A B is the mercurial syphon tube, and at W is 

 seen the glass weight or float attached to a silk cord. 

 This weight floats upon the surface of the mercury 

 rising or falling in the tube in accordance with the 

 movement of the mercurial column; by the side of 

 the syphon is a second guide tube, D, for the counter- 

 poise weight C, at P is shown the pulley over which 

 the silk cord passes giving movement to the index hand 

 over the Dial as previously described. 



At the side of the diagram we show a wire plug, E, 

 used for making these barometers portable for travelling 

 or exportation. It is simply a stiff wire covered witb 

 cotton throughout its whole length, and as will be 

 seen in the drawing, it has sufficient cotton woand 

 round the lower end to fit the mercurial tube tightly at 

 two points, 



TO MAKE THE DIAL BAROMETER PORTABLE. 



146. By inclining the Barometer the mercury 

 is caused to fill the tube entirely, the float is then with- 

 drawn from the mercurial tube W (carefully avoiding 

 disturbing the silk cords, most of Negretti and 

 Zambra's Barometers are now fitted with a brass 

 clamp to secure the cords), and then the plug E is 



FIG. 135. forced slowly down the tube until the mercury is 



perfectly secured. The glass float being placed at the side of the syphon and 

 secured with a little soft packing carefully placed round it and the glass tubes, 

 the instrument is now made portable or secure for transit. 



We need hardly point out that the Dial Barometer must not be regarded 

 as an instrument of precision, but simply as a weather indicator or household 

 Barometer. 



Instructions for setting the Barometer in action will be sent with each 

 instrument if it has been made portable. 



The absolute height of the Barometer, at any moment, does not always indicate present 

 weather. The rise or fall of the mercurial column supplies the information of coming 

 weather or change. 



A rapid rise or fall indicates changeable and unsettled weather. 



A falling Barometer and rising Thermometer, are commonly and quickly followed by rain. 



"The longer the time between the signs and the change they foretell, the longer will 

 the altered weather last ; and the shorter between the warning and the change, the shorter 

 the continuance of the changed weather." 



" A fall, with a low Thermometer, foretells Snow." 



When the Barometer falls with the wind S.E., it is generally followed by long 

 continued Rains. 



A rapid fall of the Barometer is usually followed by much wind as well as Rain. 



For further hints How to foretell the Weather see N. and Z's. Barometer Manual, 

 compiled for them by Admiral Fixz-ROY. Price, post free, Sixpence. 



