152 NEGRETTI AND ZAMBEA, HOLBORN TIADTJCT, E.G., 



THEEIOMETEES AND HYDEOIETERS. 



AT pages 31 and 32 will be found described many important improvements in the 

 construction of Thermometers invented and Patented by NEGRETTI AND ZAMBRA. 

 Also the process for Engine- dividing the Scales and Tubes, for which a Prize 

 Medal was awarded to NEGRETTI AND ZAMBRA at the Great Exhibition of 1851 

 (see fig. 31) ; a second award of Two Medals in 1862, for many important im- 

 provements and inventions ; a Prize Medal, Santiago, Chili, 1875 ; and also a 

 Prize Medal for Thermometers, Philadelphia, 1876. Paris, 1878, Gold Medal; 

 London, 1883, Fisheries Exhibition, 2 Gold Medals, 1 Silver, 1 Bronze. 



These inventions are applied to all of NEGRETTI AND ZAMBRA'S instruments 

 enumerated in the following List, where precise accuracy is desirable. 



This List will comprise Thermometers of every form and description, suited 

 for Domestic, Medical, Horticultural, Scientific, and Manufacturing purposes, 

 arranged as far as practicable in separate divisions. 



Following these are arranged the various instruments used for ascertaining 

 the Specific Gravity of fluids, known under the general term of Hydrometers ; the 

 whole of the instruments found under this heading with various names showing 

 the same fact, viz., Specific Gravity, by differing scales, from the extremely light 

 and volatile ^Ethers and Paraffins to the dense and heavy Sulphuric Acid. 



In the appendix to this catalogue will be found Rules for comparing the 

 various Thermometer and Hydrometer Scales in general use. 



Many years of practical experience in the manufacture of Thermometers and 

 Hydrometers in every variety of shape enables NEGRETTI AND ZAMBRA to guarantee 

 the accuracy of these instruments, as regards testing and dividing the scales ; at 

 the same time, careful attention is bestowed on their construction, to insure the 

 most improved forms combined with the greatest durability. 



The following is an extract from a letter, received by Messrs. NEGRETTI AND 

 ZAMBRA, written by Mr. Whipple, the manager of Kew Observatory, with reference 

 to some Thermometers sent down by the firm for comparison. 



" I believe I may again assert with confidence, that we have never yet had so large a 

 number of low range Thermometers pass through our hands exhibiting so high a degree of 

 accuracy at the melting point of mercury." 



