688 POPULAR SCIENCE MONTHLY. 



THE FIEST THERMOMETERS. 



By M. P. DUHEM. 



TPIE thermometer, the Abbe Collet writes, came for the first 

 time from the hands of a peasant of North Holland. This 

 peasant, whose name was Drebbel, was not, however, in fact, one 

 of those coarse fellows who know of nothing but field work; he 

 seems to have been of a diligent nature, and had apparently some 

 knowledge of the physics of the time. An ingenious inventor as 

 well as an impudent pretender, and boasting that he had discovered 

 perpetual motion, while he made great advances in the art of dyeing 

 cloths, he secured favors from James I; Rodolf II gave him liberal 

 pensions and brought him to his court; and Ferdinand II, who was 

 himself interested in the thermometer, chose him as the tutor for 

 his son. 



DrebbePs thermometer an invention which he may have bor- 

 rowed from Porta, and in which Galileo doubtless preceded him 

 was composed of a vertical glass tube ending at the top in a bulb, 

 while the lower end was plunged into a vessel filled with water or 

 some colored liquid. When the bulb was warmed, a part of the 

 air contained within it was driven back into the water and escaped 

 without. "When the air became cool again as the temperature 

 around it, the external pressure caused the liquid to rise in the tube, 

 the limit of its ascent being determined by the degree to which the 

 air in the bulb had been heated, and the tension it had acquired. 



This hardly practical apparatus was still used in Germany as late 

 as 1621. The members of the Accademia del Cimento, with their 

 active interest in all physical progress, soon substituted for it the 

 more convenient instrument which we still use. Contained in a 

 transparent bulb prolonged into a fine tube, a liquid more dilatable 

 than the bulb rose in the tube when it was warmed, and descended 

 when it was cooled. The Florentine Academy, moreover, never let 

 any physical discovery pass without trying to apply it to the heal- 

 ing art. Galileo had hardly recognized the constancy of the time 

 of the oscillations of the pendulum before the pendulum was used 

 to determine the rapidity or the slowness of the pulses of pa- 

 tients. The thermometer, made convenient and portable, became 

 in the hands of the Venetian physiologist Santorio Santori a sen- 

 sitive and precise indicator of the progress of fever. Santori's 

 writings made the instrument popular, and it was soon common in 

 the enamelers' shops as the Florence or Sanctorius thermometer. 



It is hard to imagine the interest that was excited by the indica- 

 tions of this instrument, which was declared to be " worthy of 



