38 NEGBETTI AND ZAMBHA, HOLBOEN VIADUCT, E.G., 



since been supplied. Messrs. Negretti and Zambra have invented a thermometer, the construction of 

 which is as follows : a small piece of glass is inserted in the bend, near the bulb and within the tube, which 

 it nearly fills : at an increase of temperature, the mercury passes this piece of glass ; but on a decrease of 

 heat, not being able to recede, it remains in the tube, and thus indicates the maximum temperature. After 

 reading, it is easily adjusted. Pour of these instruments I have had at work for upwards of a month, two 

 in ordinary observations, and two subject to severe tests, and all have answered admirably. Hitherto every 

 series of meteorological observations has been more or less broken by the frequent plunging of the steel 

 index into the mercury, or becoming otherwise deranged. Messrs. Negretti and Zambra have, in their 

 Maximum Thermometer, supplied a want long felt." * 



Extract from the Report of the Council of the British Meteorological Society, 

 read at a General Annual Meeting of its Members, 1852 : 



" Negretti and Zambra's Thermometer, for the determination of maximum temperature, is "one of the 

 good results of the Great National Exhibition, which proved itself, as regarded meteorological instruments, 

 a most useful exponent of the insufficiency of those sold to the general public ; this Thermometer is the best 

 which has yet been constructed for maximum temperatures, and particularly for sun observations ; for as the 

 reading is determined by the entire mercurial column being detained at its highest point by a simple con- 

 trivance within the tube, the necessity for an index is avoided, and with it the constant and distressing 

 recurrence of derangement attendant upon the employment of those generally in use. This thermometer, 

 constructed and brought into operation since the close of the Exhibition, has been for some time in the 

 hands of Members of the Council, but only recently among its meteorological contributors, from its 

 having been esteemed desirable that the Council should be well informed, by actual experiment, ot' the 

 well-working of the instrument before sanctioning its general circulation. Accordingly, in the early part 

 of the year, for some months several of Negretti and Zambra's Maximum Thermometers were subjected 

 by our Secretary to severe tests, and as the results were highly satisfactory, the Council have not only 

 viewed this instrument as an addition to the practical meteorologist, but strongly recommended its adoption and 

 general use." 



Copj from the Report of the Kew Committee of the British Association 

 1853-4:- 



" The very ingenious instrument of Messrs. Negretti and Zambra has one quality, which, as regards 

 durability, places it above every other form, of Maximum Thermometer, for when once well-constructed, it can 

 never get out of order, the observer having first satisfied himself as to its correctness, may ever after- 

 wards use it with confidence, relying that his register will not be interrupted by any of those annoyances 

 to which he may have been accustomed in other forms of this instrument." 



From E. J. LOWE, Esq., F.R.A.S., F.G.S., &c., &c., to Messrs. NEGRETTI 

 AND ZAMBRA. 



" GENTLEMEN, It affords me the greatest pleasure in being enabled to speak with praise regarding 

 your Patent Maximum Thermometer. I have used a dozen of them for some time at both my observatories, 

 and of these several since the date of their invention. In no single instance has there been any cause 

 of complaint. Within the last few months I have carefully tested them in various ways, yet always 

 with the most satisfactory results. I can therefore say with truth that your patent instrument is the best 

 Self- Registering Maximum Thermometer which has ever passed through my hands; indeed, no observer 

 can do without it." 



HlGHFIELD HOUSE OBSERVATORY, NEAR NOTTINGHAM. 



FIG. 41. 



49. Negretti and Zambra's Patent Solar Radiation Thermometer 

 (fig. 41). Consists of a mercurial thermometer with a blackened bulb, the 



* The thermometers have now been used with equal satisfaction for thirty-five years. 



