I. MEASUREMENT. 393 



1757e. Memoir written by Don Eduardo Saavedra upon 

 several Arabic astrolabes existing in Spain, published in the 

 " Museo Espanol de Antiguedades." 



Archaeological Museum, Madrid. 



1757f. Bronze Astrolabe, without date or maker's name, 

 and was probably made in Italy in the 16th century. 



Ministry of Marine, Madrid. 



1758. Two Astrolabes, with four double sights ; belonging 

 to H.H. the Prince of Pless. The Breslau Committee. 



1759. Astrolabe, with movable sun-dial; belonging to H.H. 

 the Prince of Pless. The Breslau Committee. 



32. Astrolabe of Lord Dudley. 



The Royal Institute of" Studii Superiori" Florence. 



Robert Dudley, Duke of Northumberland, spent many years of his life at 

 the Florentine Court. Pie died on the 6th of September 1649, at Florence. 

 Although not an Italian instrument, his astrolabe is exhibited as a mark of 

 courtesy to England. 



Astrolabe of a Florentine author, with seven change discs, one 

 of them with a geographic planisphere. 



The Royal Institute of " Studii Superiori" Florence. 



Astrolabe of an Italian author, with a planisphere of Rojas. 



The Royal Institute of " Studii Superiori" Florence. 



Astronomical Ring of Ignazio Danti, a celebrated astronomer 

 and mathematician of Perugia. 



The Royal Institute of fi Studii Superiori" Florence. 



Fra Ignazio Danti, a Dominican, erected, under Cosimo I. (1537-1564), 

 an armillaiy circle and a sun-dial, which are yet to be seen, on the fa9ade of 

 the Church of Santa Maria Novella in Florence. 



1760. Arabian Planisphere. Royal Museum, Cassel. 



A small apparatus, of Arabian origin, remarkable for its great age and 

 comparatively good workmanship. It is in the form of a plate made of brass, 

 16 c.m. in diameter, provided with means for hanging up, and has a movable 

 alhidada. The front side shows a planisphere, the back various divisions and 

 tables covered everywhere with Arabian characters. On nine transposable 

 and one fixed plate can be shown 19 different planisphere drawings for 

 the same number of polar altitudes. 



1761. Combined Planisphere and Astrolabe. 



Royal Museum, Cassel. 



A very strong plate of brass, 37'5 cm. in diameter, with an arrangement 

 for free suspension. On the one side is a planisphere with web, on the other 

 an astrolabe with double sight. The instrument dates from the 15th or 

 16th century. 



1762. Astronomical Circle, after Gemma Frisius, made in 

 1572, by Gualtherus Arssenius, grandson of Gemma Frisius. 



H. G. Van de Sande Bakhuyzen, Director of the Observa- 

 tory, Leyden. 



