'3* Jupiter^s Moons.-^Lummotis InfeBs. 



muft pevccive, that, without the affiflance of fome other luminary befides the fun, total 

 darknefs would be the lot of his inhabitants for nearly five hours in every ten. — Again, 

 if we confuler that Jupiter's year, or periodical revolution, contains 4332 d. 8 h. 51I min. 

 of our time, or 22936,43+ of his own days, and that he has no fenfible change of feafons, 

 by reafon of the nearly perpendicular direftion of his axis, the inclination of which is only 

 1° 20', we muft fee that the number of his days in his year might frequently be loft, with- 

 out fome intermediate remembrancers between thofe two very diftant extremes : accord- 

 ingly, the Omnipotent Father of the creation has provided a remedy for thefe inconve- 

 jiiences : he has furnilhed Jupiter witli thefe four moons to cheer his inhabitants with 

 light in the frequent abfence of the fun's rays, and to prefent them with four diflerent 

 kinds of months, like our years, months, and weeks. 



Of the firft kind of months in Jupiter's year there are 244,97+, ^'^'^^ of which con- 

 tains 9,36+ of his days ; of the fecond kind there are 121,89 + , each containing i8,8i + ; 

 of the third kind there are 60,45+, each comprifing 37,94+ -, and of the fourth kind 

 there are only 25,85 +, each of which comprifes 88,68 + of his days ; fo that each fliorter 

 month, particularly of tlie three firft kinds, is very nearly double the next longer; and may 

 be confidered as exa£i:ly fuch, in counting time by divifions and fubdivifions of months, by 

 the help of intercalary days. 



But befides thefe ufes of Jupiter's fatellltes, and others, perhaps, which our limited ca- 

 pacities can never comprehend, there are three very confiderable advantages, which the 

 inhabitants of our globe poflefs, accruing from the obfervations which have already been 

 made upon them ; viz. an accurate knowledge of the parallax of the earth's annual orbit ; 

 of the real velocity of light ; and of an eafy method of afcertaining the longitude of places 

 by land ; all which are explained in the different books upon aftronomy : — fo true is it 

 throughout the whole graml fcale of nature, that no individual part is without its 

 utility. 



Lincoln, 

 March 10, 1798. 



VI. 



ObjeBions to the Opinion of ProfeJJor Spallanzani refpeEiing the Caufe of the Light of Natural 

 Phofphori. Communicated to Mr. John Fabbroni, Sub-DireBor of the Royal Mufeum of 

 Florence. By M, Jo AC HIM CarRADORI, M: D* 



XJlT length the hypothefis of Gcsttling is entirely deftroyed, in confequence of the 

 refutations of various celebrated authors, and among them Spallanzani. You may perhaps 

 rccolleft that I foretold its fhort duration, and I pointed out to Brugnatelli, at its firft ap- 

 pearance, feveral proofs of its falfity, which might be deduced from the very experiments 

 it was built upon. 



Though the refutation ofSpallanzanifhas not the merit of being the firfl, its excellence 



* Annates de Chimie, xxiv. 1 1 6. 



t Chiraico Efame del CUtadino Spallanzani. Modena, i79<>< 



canoofr 



