64 Proceedings of Philosophical Societies, [Jan. 



thai motion is upon concentric rollers, round a central pivot. 

 The stand or frame, though simple in its construction, cannot be 

 very intelligibly described without a model or a diagram. The 

 tube of the telescope is elevated to the required altitude by a 

 winch and tackle of pulleys. The gallery in which the observer 

 stands is adapted to the proper height by a similar winch and 

 tackle ; and to prevent accident from the breaking of the ropes, 

 it is supported at each side by two moveable bars that fall into 

 the steps of the ladders, which constitute a part of the frame. 

 The lower end of the tube rests upon two rollers, and at great 

 altitudes moves forwards, so that the tube itself is capable of 

 adjustment to all positions, from that, which is nearly horizontal 

 to that, which is nea/ly vertical. Without quitting the gallery, 

 the observer can move the tube both horizontally and vertically 

 upwards of 10°, and can with the utmost readiness (indepen- 

 dently of an assistant) direct the telescope to any point in the 

 heavens. All the motions are effected by means of a very few 

 cords, pulleys, and winches. The diameter of the speculum is 

 fifteen inches, and the focal length twenty- five feet. The eye- 

 pieces, which are adapted to magnify the image, possess powers 

 varying from 100 to 1500; and there are proper diaphragms to 

 modify the redundancy of light. The mode of observing is by 

 the " front view." 



Mr. Raniage exhibited to the Society, besides a neat model 

 of the tube and apparatus, two speculums ; one of fifteen inches 

 diameter, belonging to the telescope described, and another of 

 twenty-one inches diameter and fifty-four feet focus. 



There was next read a paper on the subject of Parallaxes, 

 taking the word in an enlarged sense, by M. Littrow. It was 

 in the excellent treatise of Lagrange on the determination of the 

 solar parallax, from the observed transits of the inferior planets 

 over the sun's disc, where the rectangular co-ordinates were 

 first employed, instead of the less convenient expressions of 

 spherical trigonometry, for the purpose of deducing the apparent 

 station of a planet from its longitude and latitude. The process 

 has been since improved by Olbers, Bessel, Rhode, &c. But 

 M. Littrow regards it as susceptible of siill further improve- 

 ments, which he has here exhibited. He gives the analytical 

 solution of several problems ; viz. 



1. To determine the apparent longitude and latitude of a star, 

 from the true 2:eocentric lonoitude and latitude. 



2. To solve the mverse problem. 



3 and 4. The solution of the preceding problems by series. 



5. To find the apparent right ascension and declination, from 

 their true magnitudes, and vice versa. 



6. To determine the apparent azimuth and altitude, from their 

 true magnitudes, and vice versa. 



1 and 8. To find the true place of the star, from its apparent 



