Hiflory of AJlronomy for the Year 1 8o r . 115 



Ceding and the fecond. There is a diaphragrq of 14 lines 

 between the firft and the fecond eye-glafs, at the diftance of 

 2 inches from the former, and 3 from the fecond. This 

 telefcope magnifies only five times, but it has a field of four 

 degrees. One of the fame kind may be conftrufted for 70 

 or 80 francs. 



B'.irckhardt alfo has calculated the orbits of the comets 

 of 1763, 1771, and 1773; and for the fecond he has found 

 a hyperbolic orbit. 



The comet which Meffier difcovcred on the 14th of June 

 1770, refpcfting which Burckhardt made lone; and learned 

 calculations, feenis to have a fmali circular orbil of five years 

 feven months. However, this comet was not feen before 

 1770, nor has it appeared fince. This can be afcribed only 

 to great changes in its orbit. 



Kluft we then, after having afrcrted, in the 18th century, 

 that all the comets return, afi'ert in the 19th that comets do 

 not return, that of 1759 excepted.? 



On this account I no longer think but of comets; I fpeak 

 of nothing but comets; and the onlv thing I recommend to 

 tny corrcipondents is to fearch for them, as I write to them 

 that the only thing wanting to alh-onomy is the knowledge 

 of thcfe bodies. 



On the 15th of May I had the pleafure of receiving the 

 firft copy of mv Hi/iolrf. Cchjle Frini^oije, the fruit of twelve 

 years laoour^ which terminates the 50,000 ftars, on which my 

 nephew jMichel Lefran(;ois has emploved the be(t part of his 

 youth. It contains alfo obfervations made by D'AgeletJje- 

 fore he fet out on his voyage round the world ; and thofe by 

 which Darquier, aged 83 years, terminated his glorious aftro- 

 nomical career. 



The obfervations of Tycho, Flamfteed, Picard, Lacaille, 

 and Mafl:elyne, have been the foundation of all the progrefs 

 made in aftronomy. The moft profound theories and the 

 nioft learned calculations cannot do without them, and can- 

 not difputc with them in regard to importance or duration. 

 Obfervations alone will furvive us; and obfervers, whom 

 mankind too often alful-t to undervalue, may coiifole them- 

 fclves, that they will be the only allronomers to whom, long 

 after their death, the praifcs and gratitude of our fuccellors 

 and of polit-rity will be addrefled. 



Lefran9ois Lalaude, my nephew, continues his oirerva- 

 tions, together witii the calculation of 3000 lieelinalions and 

 1000 right afccnfions of the principal liars, c.u-l) obf-rveu 

 fcveral tunes. Thelc long and p^intul labours have obtained 

 for this able obfcrvcr a place in the National Inftitute. On 

 II % the 



