4 i8 SCIENCE PROGRESS. 



known Six's maximum and minimum thermometers were 

 described {Phil. Trans., vol. lxxii., p. 72), and in 1790 and 

 1 794 respectively, the maximum and minimum thermometers 

 of Rutherford were introduced {Trans. Roy. Soc. Ed., vol. 

 iii., p. 247, 1794). In 1826 Blackadder {Trans. Roy. Soc. 

 Ed., vol. x M p. 2>Z7) introduced a registering thermometer 

 in which clockwork was used. It may be mentioned that a 

 seventeenth century thermometer, somewhat resembling 

 that of Six, is in existence among the instruments of 

 the Florentine Academy. 



So much for the history of the thermometer as far as 

 the commencement of the present century. Many of the 

 works quoted are not readily accessible, but those bearing 

 on the improvements which have since been introduced may 

 be easily found in our scientific libraries, and the reader may 

 follow the process of evolution from the imperfect instru- 

 ments before described, to the Baly and Chorley thermometer 

 in which mercury is replaced by a fusible alloy of potassium 

 and sodium for determining temperatures above the boiling 

 point of mercury, and the Le Chatelier pyrometer and the 

 modification of it introduced by Professor Roberts-Austen 

 for the determination of the high temperatures reached in 

 furnaces. 



George T. Hollow ay. 



