534 



NATURE 



{April T, 1 88 1 



positions well indicated in the middle of the sixteenth 

 century. These spheres, which constitute documents of 

 great importance historically, were recently discovered at 

 the Brussels library through a folio pamphlet bought in 

 1 868, and have been reproduced with great accuracy, by 

 M. Malou. 



The objects exhibited are carefully classified in glass 

 cases, so that they can be examined by the visitor with- 

 out being touched. In the first case, which is set apart 

 for optical instruments, is observed Fresnel's great lens ; 

 also some of the object-glasses made use of by Cassmi, 

 and other valuable objects presented to the Observatory 

 by Mme. Laugier, such as the optical apparatus made 

 use of by Arago ; the photometer, prismatic mirrors, and 



the polarimeter, by means of which the great astronomer 

 enriched science with so many beautiful discoveries. 



The second case contains objects relating to the history 

 of the " metric system," comprising a standard metre and 

 several curious specimens of foreign measures. The 

 other glass cases, arranged in a circle round the room, 

 contain various astronomical instruments, among which 

 we may mention the apparatus made use of by M. Cornu 

 to measure the velocity of rays of hght, a large theodolite 

 of Rigaud, another of Bruner, one of the first sextants 

 ever constructed ; also several instruments of more 

 modern date, the first portable meridian circle of M. 

 Mouchez, Gambey's theodolite, &c. 



The case in the centre of the room is especially 



-Aerial telescope of the 



th century, after Hevelius, from an engraving in the new Astronomical Mu 



I of the Observatory of Paris. 



noticeable : it contains a curious collection of German 

 instruments of the sixteenth century, in perfect preser- 

 vation. The attention is at once attracted by several 

 instruments of gilt brass, most artistically carved, which 

 were made at Nuremberg in the sixteenth century. 

 Amongst them we observed a curious mechanical ar- 

 rangement for casting dice, which was probably used 

 for some demonstration of the doctrine of proba- 

 bility and chances ; a valuable sun-dial of carved brass, 

 dated 1578, full of groups of allegorical personages; 

 a species of altazimuth ; a handsome repeating-circle, 

 highly ornamented, and bearing the two-headed eagle of 

 Germany;; some astrolabes, quadrants, mariner's-com- 

 passes, a small ivory sun-dial of the sixteenth century. 



presented by M. Eichens. The history of all these 

 instruments except the last is unknown ; but it is sup- 

 posed that they were either presented to Louis XIV. or 

 are what is left from the spoil of the First Empire 

 having escaped the notice of the Allies in 1815. 



On the lower part of this case are shown photographs 

 of old engravings representing the astronomical instru- 

 ments of former ages. C ne of those curious pictures is 

 reproduced above (Fig. 2), showing the astronomical 

 telescope with a simple object-glass of long focus which 

 was constructed in the seventeenth century, and of which 

 an engraving was published by Hevelius. It may serve 

 to convey an idea of the^ingular and gigantic instruments 

 which astronomers of bygone times made use of. 



