NEGEETTI AND ZAMERA, HOLBOEN YIADUCT, F.C., 



Mr. Southall varying from 216 to nearly 232 degrees of temperature. In 

 fact Mr. S. states he has, with this apparatus, caused Water to loil rapidly by 

 Solar Heat. 



Negretti and Zambra's Patent Maximum Thermometer will be found 

 eminently suited for experiment with the Helio-Pyrometer, as there is no fear 

 of the thermometer being spoilt by derangement of the index, as is the case 

 with both Rutherford's and Phillips's instruments. 



Price of complete Apparatus with N. and Z.'s Patent Maximum Thermometer 220 

 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 temperature, 

 and particularly for Sun observations. 



FIG. 51. 



FIG. 52. 



61. Pyrheliometer (Pouillett's) (fig. 51), for ascertaining the effect of 

 the sun's heat upon a given area by the number of degrees of heat imparted 

 to mercury in five minutes. Price, 550 



This instrument is composed of a shallow cylinder of steel, A, fig. 51, 

 which is filled with mercury. Into the cylinder a thermometer, D, is introduced, 

 the stem of which is protected by a piece of brass tubing. We thus obtain 

 the temperature of the mercury. The flat end of the cylinder is to be turned 

 towards the sun, and the surface, B, thus presented is coated with lamp black. 



