45, CORNHILL, B.C., AND 122, REGENT STREET, W., LONDON. 53 



NEGRETTI AND ZAMBIA'S 



PATENT HOURLY RECORDING THERMOMETRICAL APPARATUS. 



An instrument for obtaining automatic thermometer readings 

 at stated intervals of time having long been sought for after many 

 experiments, NEGRETTI & ZAMBRA have invented and constructed one 

 both simple and accurate. 



74. Negretti & Zambra's Patent Hourly Recording 

 Thermometrical Apparatus. This new instrument consists of 

 twelve Thermometers, mounted on a suitable stand, a good Clock, 

 and a Galvanic Battery. The advantages are simplicity of 

 manipulation, both in taking the recorded readings and setting the 

 thermometers for future observations ; the most important one, being 

 able to expose the thermometers at any distance from/ the clock and 

 battery the only limit being the length of the conducting wires 

 and the strength of the battery. 



Before describing the mechanical and electrical arrangements of 

 the apparatus, we proceed to explain the construction and action of 

 the thermometers themselves. This will be best understood by 

 reference to the engraving, fig. 63. 



The bulb is cylindrical, and Mercury is the thermometrical fluid. 

 The neck of the bulb is contracted at A, and upon the shape and 

 fineness of this construction the success of the instrument depends. 

 Beyond A the tube is bent, and a small catch reservoir is formed at B, 

 for a purpose to be presently explained. At the end of the tube a 

 small r.eceptacle, C, is provided. When the bulb is downward it contains 

 sufficient mercury to fill the tube and a part of the reservoir, 0, leaving suf- 

 ficient space in C for the expansion of the mercury. In this position no scale 

 would be possible, as the apparent movement of the mercury would be con- 

 fined to the space C. When the thermometer is held bulb upward, the 

 mercury breaks off at A, and by its own weight flows down the tube, filling 

 C and a portion of the tube above C, in relation to the existing temperature. 

 The scale accordingly is made to read upwards from C. To set the instrument 

 for observation, it is only necessary to place it bulb downward, then the 

 mercury takes the temperature just as an ordinary thermometer. Whenever 

 the existing temperature is required, all that has to be done is to turn the 

 thermometer bulb upward ; the mercury will then break off at A, falls to 



