NEGRETTI AND ZAMBRA'S 

 SELF-RECORDING ANEROID BAROMETER. 



FIG. 29. 



35. These Instruments are arranged to show the various fluctuations 

 that have taken place in the Barometer during the absence of the observer. 

 They consist of a carefully finished Aneroid, and an eight-day Clock ; between 

 these is placed in a vertical position, a revolving cylinder having a metallic 

 paper attached to it ruled to coincide with the inches and tenths of the 

 barometer scale. Close to this paper, is a pencil mounted on a metallic rod 

 and is moved up 'and down as the variation of atmospheric pressure acts upon 

 the vacuum chamber of the Aneroid ; at every hour this pencil is made to mark 

 the paper by simple mechanism in connection with the clock. 



By this means a black dotted curved line is produced on the paper, show- 

 ing at a glance the present height of the barometer whether it is falling or 

 rising for how long it has been doing so, and at what rate the change has 

 taken place if falling or rising at the rate of one-tenth of an inch per hour, or 

 one-tenth in twenty-four hours ; all of which are particulars most essential to 

 know when foretelling the weather, and which can only be obtained from an 

 ordinary barometer by very frequent and regular observations. 



Our engraving (fig. 29.) shows the full mounting of the Registering 

 Aneroid, combining a reliable Timepiece with an exceeedingly interesting 

 Meteorological Instrument, of a suitable and convenient size for a library or 

 dining room mantel-shelf. 



Recording Aneroid Barometer with Thermometer, ag shown fig. 29 



Price, 22 



Large size ditto ditto with more Ornamental Mounting . 27 10 



Haled charts for the above, per Hundred ...',. 110 



