OF METEOROLOGICAL INSTRUMENTS. 



rig. 24. 



Fig. 26. 



Fig. 25. 



STANDARD THEBMOMETEKS. 



Besides the precision with which thermometers may be graduated, where excellence 

 is wanted, the greater part really depends on the care and skill employed in constructing 

 the tube. In this respect L. CASELLA has much pleasure in referring to the guarantee 

 afforded by his name, as well as that most critical test, viz., his well-known success in 

 constructing thermometers for mountain measurement, as also his self-registering ther- 

 mometers for clinical purposes ; with which he believes he almost exclusively supplies 

 the profession, and was alone identified with them full five years before they were 

 adopted for general use. At the Exhibition of 1862, L. CASELLA obtained the only 

 prize medal for registering meteorological instruments. 



23. Independent OP Natural Standard Thermometer^ engine divided on the stem, 



the internal diameter of the bore being carefully calibrated, and the exact 

 value of all its parts further determined by comparison at the freezing and 

 boiling points of water . . . . . 550 



24. STANDARD THERMOMETER, COMPARATIVE, carefully tested in all its parts, tube 



15 inches long, engine divided on the stem, and figured on raised metal or 

 porcelain scale, to 215 Fahrenheit, or 102 centigrade, in maroon case, with 

 verification from the Royal Kew Observatory (fig. 24) . 250 



