20 



HEAT. 



Mr. Wedgewood observed that the heat 

 which raised the temperature of Fahr- 

 enheit's thermometer from 50 to 2 12, 

 expanded a piece of silver from to 8 

 of a certain scale, and that a heat which 

 expanded the silver from to 66 of its 

 scale, corresponded to 2 of the clay or 

 Wedgewood's scale. By these and si- 

 milar experiments, he found that each 

 degree of his Pyrometer is equal to 130 

 of Fahrenheit's scale. The temperature 

 of a red heat, visible by daylight, which 

 was found to correspond to 1077^, was 

 taken as the commencement of Wedge- 

 wo'od's scale. 



The following TABLE, pointing out 

 the effects upon bodies of different de- 

 grees of heat according to this and Fahr- 

 enheit's scales is taken from Murray's 

 System of Chemistry. 



Wedg. Fahren. 

 Extremity of the Scale of 



Wedgwood's Thermometer 240 32277 

 Greatest heat of an air fur- 

 nace, 8 inches in diameter, 

 which neither melted nor 



softened Nankin porcelain 160 21877 

 Chinese porcelain softened, 



best sort 156 21357 



Cast iron, thoroughly melted 150 20577 



Hessian crucible, melted 150 20577 



Bristol porcelain, not melted 135 18627 



Cast iron begins to melt 130 17977 



Greatest heat of a common 



smith's forge 125 17327 



Plate glass furnace, strongest 



heat 124 17197 



Bow porcelain, vitrifies 121 16807 



Chinese porcelain, softened, 



inferior sort 120 16677 



Flint glass furnace, (strongest 



heat) 114 15897 



Derby porcelain vitrifies ... 112 15637 



Chelsea porcelain vitrifies .. 105 14727 



Stone ware baked in 102 14337 



Welding heat of iron (great- 

 est) 95 13127 



Worcester porcelain vitrifies 94 J3297 



Welding heat of iron (least) 90 12777 



Cream-coloured ware baked in 86 12257 

 Flint glass furnace (weak 



heat) 70 10177 



Working heat of plate glass 57 .8487 



Delft ware baked in 41 6407 



Fine gold melts 32 5237 



Settling heat of flint glass . . 29 4847 



Fine silver melts 28 4717 



Swedish copper melts 27 4587 



Silver melts (Dr. Kennedy). . 22 3937 



Brass melts 21 3807 



Heat, by which enamel co- 

 lours are burnt on 6 1857 



Red heat, fully visible in day-light 1077 



Iron red hot in the twilight 884 



Heat of a common fire 790 



Iron bright red in the dark 752 



Zinc melts, .,,.,,,, 700 



Fahvcn. 



Quicksilver boils (Irvine) 672 



(Dalton) 660 



(Crichton) 655 



Lowest ignition of iron in the dark 635 



Linseed oil boils 600 



Lead melts (Guy ton, Irvine) 594 



Sulphuric acid boils (Dalton). . . . 590 

 The surface of polished steel ac- 

 quires a uniform deep blue. . . . 580 



Oil of turpentine boils 560 



Sulphur burns 



Phosphorus boils 554 



Bismuth melts (Irvine) 476 



The surface of polished steel ac- 

 quires a pale straw-colour 460 



Tin melts (Crichton, Irvine) 442 



A mixture of three parts tin and 

 two of lead melts; also a mix- 

 ture of two parts tin and one of 



bismuth melts 334 



A compound of equal parts of tin 



and bismuth melts 



Nitric acid boils 242 



Sulphur melts ; 226 



A saturated solution of salt boils 218 

 Water boils (the barometer being 

 at 30 inches); also a compound 

 of five of bismuth, three of tin, 



and two of lead melts 212 



A compound of three parts of tin, 

 five of lead, and eight of bis- 

 muth, melts rather below 210 



Alcohol boils 1 74 



Bees' wax melts 1 42 



Spermaceti melts 133 



Phosphorus melts 100 



Ether boils 98 



Heat of the human blood 98 



Medium temperature of the globe 50 



Ice melts 32 



Milk freezes 30 



Vinegar freezes at about 28 



Strong wine freezes at about .... 20 



A mixture of one part alcohol and 



three parts water freezes 7 



A mixture of alcohol and water in 



equal quantities freezes 7 



A mixture of two parts alcohol 



and one part water freezes .... 1 1 

 Melting point of quicksilver (Ca- 

 vendish) 39 



Liquid ammonia crystallizes 



( Vauquelin) 42 



Nitric acid sp. gr. about 1.42 



freezes (Cavendish) 45 



Sulphuric aether congeals (Vau- 

 quelin) 47 



Natural temperature observed by 



Mr. Hutchins at Hudson's Bay 50 

 Ammoniacal gas condenses into a 



liquid (Guyton) 



Nitrous acid freezes 56 



Cold produced from diluted sul- 

 phuric acid and snow, the ma- 

 terials being at the temperature 



of 57 78 



Greatest artificial cold yet mea- 

 sured (Walker). .,,,, -91 



