78 



NEGKETTI AND ZAMBEA, HOLBOBN VIADUCT, B.C., 



FIG. 87. 



103. Negretti and Zambra's Self-Kecording Hygrometer, fig. 87. 

 The Thermometers in this Hygrometer are similar in construction to those used 

 in Negretti and Zambra's Patent Hourly Recording Thermometric Apparatus. 

 No. 64, Page 55. It will be seen by the drawing (fig. 87) that two 

 Thermometers are, with a Water Cistern, mounted upon a metal frame in; 

 such a manner that they will fall over and become inverted from the joint 

 action of a Clock and Galvanic Battery. 



The most important improvement in this Self- Recording Hygrometer is 

 that it can be freely exposed at any distance from the regulating clock. Our 

 wood engraving exhibits the Clock, A, with an adjusting index upon its dial, 

 enabling the observer to arrange the release of the detent, B, at any appointed 

 time, thus allowing the frame supporting the Hygrometer to turn over, and 

 by inverting the Thermometers record the temperature of both the Wet and 

 Dry bulb instruments at the moment. 



The escapement is an Electro Magnet, seen at B, in connection with a 

 Galvanic Battery, B, the Clock at C and C, and the Wire A and A. At the 

 arranged time the circuit is completed by the clock, and the electrical current 

 acting upon the soft iron magnet releases the detent and the Hygrometer 

 turns over. 



The instrument is re-set for another observation, by turning back the 

 frame with the Thermometers into its original vertical position (as shown in 

 the engraving) and by adjusting the index of the Clock. Price 10 10 



The peculiar construction of the two Thermometers is fully described 

 on page 63, and fig. 71. 



