108 Mijlcry of AJlronomy for the Year 1799. 



has a compenfation balance, according to the principles ex- 

 f)lained in the fame volume of the Blbliotheque Brltannique* . 

 It is moved by a fpiral fpring rolled up in the form of a cy- 

 linder. The efcapcmeut 'm defcribcd in the fame work, and 

 illuftrated with figures. All the frictions, both of the efcape- 

 nicnts and the parts of the machine, are performed on rubies 

 either plain or pierced ; and this eflential improvement, 

 which renders the ufe of oil unneceflary, had never before 

 been carried to the fame degree of perfection. 



Thefe able artirts improved themfelves by a refidcnce of 

 feveral years at Paris with Ferd. and Louis Berthoud : they 

 afterUards united their talents at Geneva, to " the great ad- 

 Vantage of an art in which they have fo eminently diftin- 

 guilhcd themfelves. C. Magnin is now travelling through 

 Spain, to which he has carried a time-keeper like that above 

 defcribed. They make alfo portable chronometers, with an 

 cfcapement independent and a compenfation balance, which 

 go exceedingly well. 



'I'he art of piercing rubies, formerly carried from Geneva 

 to England by Fatio, was a fecret loll to the country' in which 

 it was invented. Thefe artilts have again naturalifed it, for 

 they cut and pierced themfelves all the rubies they employed. 



C. Louis Berthoud has alfo brought a workman to Paris, 

 and he will do the fame thing in future in regard to the 

 thronometers with which he will enrich the navy. The 

 minifier has entruflcd me with one, the exaftnefs of which 

 is of the utmoft value for the conxTpondence of the five ob- 

 fervatories of Paris. 



I hoped that my aerial voyage, on the 25th of July 1799, 

 -vVould have procured me fome knowledge refpetSling the fcin- 

 tillation of the itars and the nature of the atmofpliere ; but 

 1 was deceived by the perfon to whom I gave my confidence, 

 and for whom I braved the public opinion. I was not able 

 to afcend to a fiifficient height, but this atmofpheric prome- 

 nade enabled me to make fome ufeful remarks on aerial 

 currents. On fctting out from Tivoli the air appeared to me 

 perfcttly calm, and there did not feem to be the leaft wind, 

 yet I perceived that the balloon advanced towards the eaft. I 



'* Vol. XII. 



rofe 



