b 



578 PHILOSOPHICAL TRANSACTIONS. [aNNG 1784. 



freezing of water; 8° from the freezing of water to full ignition: and l6o° above 

 this to the highest degree I have hitherto attained. 



As we are now enabled to compare not only the higher degrees among them- 

 selves, and the lower among themselves, on their respective scales, but likewise 

 the higher and lower with each other in every stage, it may be proper to take a 

 general view of the whole range of measurable heat, as expressed both in Fah- 

 renheit's denominations and in mine; and for this purpose I have drawn up ihe 

 following little table of a few of the principal points th it have been ascertained, 

 to show their mutual relations or proportions to each other; any other points 

 that have been, or hereafter may be observed, by these or any other known ther- 

 mometers, may be inserted at pleasure. 



Fahr. Wedg. Fahr. Wedg. 



Extremity of the scale of myl 077 o () , n o Heat by which my enamel co-1 ,- 



thermometer J"*'' lours are burnt on J 18o < ° 



Greatest heat of my small air- 1 g 7 _ jg Red-heat fully visible in day-light 107/ 



furnace i Red-heat fully visible in the dark 947 — 1 



Cast iron melts 17977 1 30 Mercury boils 600 3 ^y 5 



Greatest heat of a common"! r „„. 10 , Water boils 212 6 Jlss 



smith's forge J 17 * 47 "* Vital heat 97 ? V| 



Welding heat of iron, greatest. . 13427 95 Water freezes 32 8 T ^§^ 



• least .... 12777 90 Proof spirit freezes o 8 - 2 -V_ 



l oUo 



Fine gold melts 5237 32 The point at which mercury ~) 



Fine silver melts 4717 28 congeals, consequently the ( , 



Swedish copper melts 4587 27 limit of mercurial ther- t aD0Ut 4U 6 Tore 



Brass melts 3807 21 mometers. J 



To assist our conceptions of this subject, it may be proper to view it in another 

 light, and endeavour to present it to the eye; for numbers, on a high scale, are 

 with difficulty estimated and compared by the mind. I have therefore completed 

 the scales of which a part is represented in fig. 11 and 13, by continuing the 

 same equal divisions, both upwards and downwards, as far as the utmost limits of 

 heat that have hitherto been attained and measured. In a scale of heat drawn 

 up in this manner, the comparative extents of the different departments of this 

 grand and universal agent are rendered conspicuous at a single glance of the eye. 

 We see at once, for instance, how small a portion of it is concerned in animal 

 and vegetable life, and in the ordinary operations of nature. From freezing to 

 vital heat is barely a 500th part of the scale; a quantity so inconsiderable, rela- 

 tively to the whole, that in the higher stages of ignition, 10 times as much might 

 be added or taken away, without the least difference being discernible in any of 

 the appearances from which the intensity of fire has hitherto been judged of. 

 Hence, at the same time, we may be convinced of the utility and importance of 

 a physical measure for these higher degrees of heat, and the utter insufficiency 

 of the common means of discriminating and estimating their force. I have too 

 often found differences, astonishing when considered as a part of this scale, in 



