CATALOGUE. HEAT, CHANGES OF FORM. 



399 



The thermometer it a medium stands about .48°, higher 

 immersed in water, than in st«am only, >yhich corres- 

 ponds to a difference of about .3 in the height of the 

 barometer. 



The rapidity of boiling makes little difference in the 

 keat, there are, however, sometimes irregularities of half 

 a degree or more, notwithstanding all possible precautions. 



The standard thermometer is graduated by immersion in 

 steam, when the barometer is at 29.8 : its boiling point is 

 ' " higher than that of De Luc's, who employs 28.75 for 

 the height of the barometer, immersing the bulb in water. 

 A vessel with a chimney is employed, loosely covered for 

 steam, the bulb being held 2 inches above the water. 



When the bulb is immersed, the barometer ought to 

 stand at 49.5, but when an open vessel is used, the baro- 

 meter must be at 29.8, and the thermometer must be 

 wrapped in cloths, and held upright, and hot water must 

 be frequently poured over it. Rain water or distilled 

 water must be employed. 



Corrections are given for the expansion of the scale, and 

 for the coldness of the stem ; and a diagonal scale for re- 

 ducing the effect of the height of the barometer. For 

 each inch ^j^ of the interval between the freezing 

 and boiling points must be allowed. • 

 Six on the division of thermometers. Ph, 



tr. 1782. 72. 

 Biot's thermometer. See Communication 



of Heat. 



It is simplest and most usual to reduce thermometers to 

 SO. of the barometer. 



Comparative Table of Thermometers. 



Degrees from Freezing 

 freezing to boiling, point. 



Wedgwood 



Poleni 



Amontons 



Newton 



Old Edinburgh 



Del Cimento 



sometimes 

 Reaumur 

 Sauvages 



Celsius, centigrade 

 Delisle 

 Del Cimento 



sometimes 

 Sulzer nearly as De- 

 lisle, about 

 Hales 



Delahire Obs. Par. 

 Fahrenheit 

 Ac. I'ar. old. 

 R. S. old 



1.48« 

 15.« 

 21.5 

 34. 

 38.8 



.8i 



SO 



87 

 100. 

 150 



154 



156 

 163 

 17li 

 180 

 214 



ai».s 



— 8.142 

 47.3 

 51.5 



O. 



8.2 



13.5 

 0. 

 0. 



O. 

 150 



20. 



0. 

 28 

 32 

 25 



— 73i 



Boiling 

 point. 



— fl.fiSS 

 62.9 

 73- 

 34 

 4; 



8 If 

 80 

 87 

 100 

 0. 



!?♦ 



163 

 199i 



2ia 

 as 9 



14U 



Hawksbee's was a spirit thermometer; he found the ex- 

 pansion of air at the freezing point .j,^ for each of his 

 degrees : hence his greatest summer heat, of 130°, be- 

 comes 80°, F. if we make it 84°, we shall have 450° 

 for the boiling point. 



Gaussen's comparison of the thermometers of mercury 

 and alcohol, from the experiments of Dcluc and Micheli. 



Merc. 



160 

 156 

 150 



135 



130 W. 17977 F. 



This agrees with the formula i r -f- ^;„rr. 



Micheli found 20° of the spirit thermometer agree to 

 26.4° of the mercurial, 30° to 36.?°, 40° to 46.4°, JO* 

 to 56.6°, 60° to 64.3°, and 70° to 72.4. 



Table of the Effects of Heat. 



Wedgwood's greatest heat 240° W. 



Nankeen porcelain withstands 



Best Chinese porcelain softened 



Pig iron melts completely 



Bristol porcelain withstands 



Pig iron begins to melt W. 



Iron, pure nickel, and pure cobalt melt, 



Bergman 

 Smith's forge 

 Plate glass furnace 

 Bow porcelain vitrifies 

 Inferior Chinese porcelain softens 

 Flint glass furnace 

 Derby porcelain vitrifies 

 Chelsea porcelain vitrifies 

 Storre ware, pots de gres, baked. 

 Welding heat of iron 

 Worcester porcelain vitrifies 

 Welding heat of iron begins 

 Cream coloured ware baked 

 Flint glass furnace, weak. 

 Working heat of plate glass 

 Delft ware, baked 



tcoi 



125 

 124 

 121 

 120 

 1 14 

 I 12 

 lO.'i 

 102 

 85 

 94 

 00 

 30 

 JO 

 57 

 41 



