VOL. IV.] PHILOSOPHICAL TRANSACTIONS. 403 



of the particles of quiescent solids, and in so doing calls the absolute rest of 

 bodies in question, by undertaking to prove, that some of those bodies, which 

 we think have their parts most at rest, are not exempted from having internal 

 motions in them; from which he thinks it probable, that in other bodies, 

 whose solidity is confessed inferior, the component particles are not in a state 

 of perfect rest. 



II. Del Movimento della Cometa, apparsa il mese di Dicembre 1664, Da 

 Pietro Maria Mutoli, in Pisa, in 4to. 



This author principally discourses of the motion and place of that comet, 

 and how its odd appearances may be solved. He works not by the way of tak- 

 ing the several altitudes from the horizon, but by observing the position of the 

 comet among some neighbouring fixed stars ; for doing which, he says he 

 employed only a simple thread stretched out by an arch, to make it evident 

 whether this comet had a sensible parallax, or not. From whence he concludes 

 that this comet was above the moon, as it had no parallax that was per- 

 ceivable. 



III. Erasmi Bartholini* de Cometis An. 1664, et 1665, Opusculum ; Ex 

 Observationibus Hafniae habitis adornatum. Hafnise, in 4to. 



The author having first intimated that the more narrowly this subject about 

 comets has been searched into, the farther have intelligent men receded from 

 the opinion of the peripatetics concerning them ; he acquaints the reader what 

 instruments he used in making observations; among which was a quadrant of 

 1-1- foot radius; what conveniency he had as to the place of observation ; what ob- 

 servations he made, viz. An. 1664, December 23, 24, 25, 20, 27, 28, 2(), 30, 31, 

 and An. l665, January 1, 3, 4, 5, 6, 7, 9, 12, 24, 31, and February 7. Also, 

 how he found the longitude and latitude of this comet, viz. by observing its 

 distances from two fixed stars ; and having found those, how thence he found 

 its right ascensions and declinations for every day : Besides, how he found the 

 motion of the comet in its orb, and the place of intersection and the angle of 

 inclination with the ecliptic. To which he adds his considerations about the 

 place of the comet, and the parallaxes; vindicating here the noble Tycho from 

 the accusation of Riccioli in Almag. Novo: Concluding all with an investigation 

 of the causes of comets ; where he examines whether comets be coeval with 

 the world, or produced anew; and, if the latter, how: Insinuating that, though 

 he esteems the latter comet to be different from the former, yet, admitting the 



* Erasmus Bartholin was successively professor of mathematics and philosophy at Copenhagen j 

 and attained the rank of counsellor of state. He died in 1698, at 73 years of age. He was au- 

 thor of some other mathematical and physical works, besides that mentioned in this article j as, 

 Experimenta Chrystalli Islandici, 1670, in 4to, and De Aere Hafniensi, l679, in 8vo. 



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