THE EVOLUTION OF THE THERMOMETER. 



rHE earliest thermometer appears to have been made 

 towards the close of the sixteenth century, but the 

 name of the actual discoverer is not known. The invention 

 has been variously attributed to Robert Fludd. a London 

 physician and a prolific writer on medicine and alchemy, 

 who died in 1637 ; to Galileo (prior to 1597) ; to Cornelius 

 Drebbel of Alcmar (see Boerhaave's Chemistry, translated 

 by Shaw, i., 152); to Sanctorius of Padua, and to Father 

 Paul of Cracow, who died about 1 59 1. The balance of 

 evidence appears to rest with Sanctorius, who, in his Com- 

 mentaria in Artem Medicinal em Galeni (p. 736, 161 3), 

 claims to have discovered the thermometer. John Alphon- 

 sus Borelli (De Motu Animalium, II. , 175, 1680), and 

 Malpighi {Posthumous Works, Amsterdam, 30, 1697), a l so 

 give him credit for the invention. 



All the earlier thermometers depended upon the 

 expansion of air enclosed in a bulb on the end of a tube, 

 which terminated in an open-tppped bulb containing a 

 coloured liquid, or dipped into an open vessel holding the 

 liquid. The expansion or contraction of the air was thus 

 indicated by the movement of the liquid within the tube, 

 but as the change of volume of the air was affected by the 

 atmospheric pressure, and the tube was either not graduated 

 or only marked out in divisions as the taste of the maker 

 dictated, the thermometers were of but little value. 



The first alcohol thermometer is said to have been made 

 by Galileo in 161 1 or 1612, and the "Florentine thermo- 

 meters " containing spirit of wine in a sealed tube, were 

 employed about the middle of the seventeenth century, by 

 the Academists del Cimento, and were introduced into 

 England by Boyle. In these thermometers, no attempt 

 appears to have been made to expel air before sealing them, 

 and a lucky find of a number of them in 1 829, has shown that 

 their graduation was purely arbitrary. The divisions were 

 duodecimal, each consisting of an enamel bead sealed upon 



