GALILEO. 



1 



\~ented the simple pendulum, and made 

 use of it in his astronomical experiments: 

 he had also thoughts of applying it to 

 clocks, but did not execute that design. 

 The glory of that invention was reserv- 

 ed for his son Vincenzo, who made the 

 experiment at Venice in 1649 ; and 

 Huygens afterwards carried the inven- 

 tion to perfection. Of Galileo's inven- 

 tion also was the machine with which the 

 Venetians render their laguna fluid and 

 navigable. 



" He also discovered the gravity of the 

 air, and endeavoured to compare it with 

 that of water ; and opened several other 

 inquiries in natural philosophy. He was 

 not esteemed and followed by philoso- 

 phers only ; but was honoured by per- 

 sons of the greatest distinction of all na- 

 tions. Galileo had scholars worthy of so 

 great a master, by whom the gravitation 

 of the atmosphere was fully established, 

 and its varying ^pressure accurately and 

 conveniently measured, by the column 

 of quicksilver of equal weight sustained 

 by it in the barometrical tube. The elas- 

 ticity of the air, by which it perpetua'ly 

 endeavours to expand itself, and while it 

 admits of condensation, resists in propor- 

 tion to its density, was a phenomenon of 

 a new kind, (the common fluids having 

 no such property,) and of the utmost im- 

 portance to philosophy. Thse princi- 

 ples opened a vast field of new and use- 

 ful knowledge, and explained a great va- 

 riety of phenomena, which had been ac- 

 eounted for in an absurd manner before 

 that time. It seemed as if the air, the 

 fluid in which men lived from the begin- 

 ning, had been then first discovered. 

 Philosophers were everj- where busy, 

 enquiring into the various properties and 

 their effects ; and valuable discoveries 

 rewarded their industry. Of the great 

 number who distinguished themselvs on 

 this occasion, we cannot but mention Tor- 

 jricelli and Viviani, in Italy; Pascal, in 

 France ; Otto Guricke, in Germany ; and 

 Boyle, in England." 



Galileo wrote a number of treatises, of 

 which the principal, published during his 

 life-time, besides his " Mechanics," " Ba- 

 lance," and " Dialogues," already men- 

 tioned, were, " The Operations of the 

 Compass, geometrical and military," 

 1606 ; " A Discourse, addressed to the 

 Most Serene Cosmo II. Grand Duke of 

 Tuscany, concerning the swimming of 

 Bodies upon, and their submersion in, 

 Water," 1612 : " Nuncius Sidereus," 

 1610, of which a ' Continuation," or 

 " An Essay on the Histpry of Galileo's 



last Observations on -Saturn, Mars, Venu3, 

 and the Sun, &c." was afterwards collected 

 from letters between Galileo and his cor- 

 respondents ; " A Letter concerning the 

 Trepidation of the Moon, lately disco- 

 vered, inscribed to Alphonso Antonini, 

 with Antonini's Answer," 1638 , " A Dis- 

 course of the Solar Spots, &c. with Pre- 

 dictions and Ephemerides of the Medi- 

 cean Planets," 1613 ; the famous Italian 

 piece, entitled, " II Saggiatore," written 

 in defence of Guiducci's " Discourse oh. 

 Comets," and containing a complete ac- 

 count of the physiology and astronomy 

 of our author, printed in 1623 ; " A Letter 

 to Prince Leopold of Tuscany, examin- 

 ing the fiftieth chapter of Licetus's Le- 

 theosphoros;" " A Letter to Christopher 

 Greinbergerus, concerning the Montuo- 

 sity of the Moon," 1611 ; "Mathematical 

 Discourses and Demonstrations concern- 

 ing two new Sciences, relating to Me- 

 chanics and local Motions, together with 

 an Appendix concerning the Centre of 

 Gravity in some Solids," I6o8, Sec. 



The preceding articles, together with 

 some other treatises, written either b'y 

 Galileo, or by some of his disciples, in 

 defence of his doctrines and observations, 

 were collected and published by Meno- 

 lessi, in 1656, under the title of" 1'Opere 

 de Galileo Galilei Lynceo, nohile Floren- 

 tine," &c. in two volumes quarto. Seve- 

 ral of these pieces were translated into 

 English, and published by Thomas Salis- 

 bury, in his " Mathematical Collections," 

 in two vols. folio. 



A volume also of his " Letters," to se- 

 veral learned men, and solutions of a va- 

 riety of problems, was published at Bo- 

 logna, in quarto. His last disciple, Vincen- 

 zo Viviani, who proved a very eminent 

 mathematician, methodised a piece of his 

 master's, and published it under the title 

 of" Quinto Libro de gli Elementi d'Eu- 

 clid," &c. 1674, quarto ; and he also pub- 

 lished some other pieces of Galileo, in- 

 cluding extracts from his '* Letters to a 

 learned Frenchman," in which the au- 

 thor gives an account of the works which 

 he intended to have published, and an 

 extract of a letter to John Camillo, a ma 

 thematician of Naples, concerning the 

 angle of contact Many other of Gali- 

 leo's writings were unfortunately lost to 

 the world, owing to the superstition of 

 one of his ignorant nephews; who, con- 

 sidering that his uncle died a prisoner of 

 the holy office, though permitted to reside 

 in his own house, suspected that his pa- 

 pers mightcontain dangerous heresies,and 

 therefore committed them to the flames.- 



