HEAT APPARATUS. 139 



by Giuseppe Moriani, who, for his skill in glass-blowing, was sur- 

 named II Gonna. 



Many of the readings recorded by Rinieri are to be found in 

 the Memoirs of the Academy del Cimento, but these were long 

 supposed to have lost their value, as the instruments themselves 

 could not be compared with our present thermometric scale. 



In 1829, however, a number of these very thermometers were 

 found by Antinori, and their graduations were compared with those 

 of Reaumur's scale, so that the readings of Rinieri can now be 

 interpreted. 



One of the physical researches for which the Florentine Aca 

 demy employed these thermometers, was to determine whether the 

 melting of ice always takes place at the same temperature. This 

 question they finally answered affirmatively. 



The next great step in thermometry was made by Newton, in 

 his " Scala graduum Caloris," in the Philosophical Transactions 

 for 1701, where he proposes the melting of ice and the boiling of 

 water as standard temperatures. 



Fahrenheit, of Dantzic, about 1714, first constructed thermo- 

 meters of which the graduation was uniform. These thermometers 

 were much used in England, and Fahrenheit's graduation is still 

 the most common in English-speaking countries. In Fahrenheit's 

 scale the temperature of melting ice is marked 32, and that of 

 boiling water 212. 



The Centigrade scale was introduced by Celsius, of Upsala. In 

 it the freezing point is marked o, and the boiling point 100. The 

 obvious simplicity of this mode of dividing the space between the 

 points of reference has caused it to be very generally adopted, 

 along with the French decimal system of measurement, by scien- 

 tific men, especially on the Continent of Europe. 



The scale of Reaumur, in which the freezing point is marked o% 

 and the boiling point 80, is still used for some medical and 

 domestic purposes on the Continent of Europe. 



The existence of these three different thermometric scales fur- 



