236 M. Arago on the T7iermometrical State 



Pliny's house was not situated on high ground. He expressly 

 says that it lay near the Apennines, at the foot of a hill not 

 far from the Tiber. We must look to the inhabitants of the 

 city of CasteUo^ the ancient Tifernus, to decide whether, as I 

 believe, the climate is now more temperate than in the time of 

 Pliny. At all events, it may be well to notice if the surround- 

 ing mountains be still covered with lofty and ancient woods. 



We shall now proceed to modern Tuscany. 



As soon as Galileo had, towards the end of the sixteenth cen- 

 tury, discovered the thermometer, the academicians Del Cimento, 

 caused a great number of these instruments to be constructed 

 perfectly similar to one another. These thermometers having 

 been sent into various towns of Italy, were useful in supplying 

 simultaneous meteorological observations. At this time the 

 Grand Duke of Tuscany, Ferdinand II., employed the monks 

 of the principal convents situated on his states, to aid in these 

 interesting researches. The enormous mass of documents which 

 had been thus collected were dispersed, at a time when, to ob- 

 tain a Cardinal's hat, Prince Leopold de Medicis sacrificed the 

 Academy del Cimento to the resentments of the Papal Court. 



A few volumes only escaped, in a wonderful manner, from 

 the vandalism of the agent of the Inquisition. Amongst them 

 was a part of the observations made by the father Raineri, at 

 the convent Des Angeli of Florence. These observations, com- 

 pared with those of modern meteorologists, seem likely, on ac- 

 count of their antiquity, to throw light on the question of the 

 change of climate. But, unfortunately, the thermonieters of the 

 academicians Del Cimento had no fixed term ; and different at- 

 tempts, intended to establish the accordance of the degrees of 

 this instrument, with those of Reaumur and Fahrenheit, only 

 shewed that many more were still desiderated. 



Such was the state of matters, when, in 1828, a box was dis- 

 covered at Florence, which, among many other old instruments, 

 contained a great number of the thermometers of the Academy 

 del Cimento, divided into a scale of fifty parts. Mr Guillaume 

 Libri to whom they were entrusted, and it would have been diffi- 

 cult to place them in better hands, began by ascertaining that they 

 all agreed with each other. Then, with the help of more than 

 200 comparative observations, he compared their scale with the 



