History of Astronomy for the Year 1803. 1$ 



the establishment of the decimal measures ; the more ne- 

 cessary as Italy had in its measures an inexplicable variety, 

 as may be seen in my Travels in Italy, ^u 



The king of Spain has ordered a map of his states to be 

 constructed by a body of geographical engineers, under the 

 direction of M. Ximencs. We have already maps of al) 

 the coasts ; but it will require a long time to survey the in-' 

 terior. M. Chaix, an able Spanish astronomer, will be the 

 first co-operator. M. Megnie, an ingenious mathematical 

 instrument maker, has settled at Madrid, and will furnish 

 the necessary instruments. . g 



The king of Prussia and the elector of Saxony,, desirous 

 ©f having maps of their states, M. Von Zach, who is at 

 the head of this labour, will take advantage of it to measure 

 a degree of longitude which is still wanting notwithstanding 

 the efforts made for that purpose by Cassini. 



Since the longitude of Brest and Manheim is known, it 

 appears to me, that, by applying the measurements made in 

 France, we might have the 13° of longitude which there are 

 under the 49th parallel to a six hundredth part, or 60 toises 

 nearly for a degree; but we ought to obtain greater precision, 

 and the chief of the state waits only for peace to procure 

 to the sciences this new benefit. 



In the month of August, Baron Von Zach established 

 himself with Brug on the mountain called the Brocken, at 

 the height of 550 toises. He made signals with gun- powder 

 from the top of a tower ; they were seen at the distance of 

 thirty-three leagues. The astronomers took different posts, 

 and they were joined by Prussian officers, who served an ap- 

 prenticeship at Gotha. They were provided with sextants, 

 artificial horizons, achromatic telescopes', and chronometers. 

 They were able to take corresponding heights within half a 

 second, and they observed by their chronometers the signals 

 made by night, and by day at convenient moments. M. 

 Von Zach kindled only half a pound of gun-powder each 

 time. In the day the explosion and flame were seen at the 

 distance of thirty-three leagues, by means of a small com- 

 mon telescope, which magnified only twenty times ; in the 

 night they were seen by the naked eye. The duchess of 

 Gotha, who is short-sighted, saw these fires in her garden, 

 between nine and ten at night, without the assistance of a 

 telescope \ thev appeared like lightning, though the di- 

 stance is nearly twenty -three leagues in a straight line. The 

 principal places which baron Von Zach has determined, and 

 where there are observers, are the towns of Magdebourg, 

 Halberstadt, yuidiembourg, Bernberg, Coetheji> Dessau, 

 BET l Casseij 



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