438 SEC. 11. ASTRONOMY. 



Ancient Sundial with Planetary Arrangements erected 

 by Charles II. in the gardens of Whitehall Palace. 



Gardner Collection. 



1919a. Apparatus consisting of Thermopiles and 

 Concave Mirrors employed in measuring the Moon's 

 radiant heat. Earl of Rossc, F.R.S. 



The reflecting mirrors were made alternately to receive the moon's image 

 formed by the speculum of the three-feet telescope at Parsonstown, and the 

 heat was concentrated by each in succession on the face of the corresponding 

 thermopile, of which the diameter is about half an inch. The thermopiles 

 are inserted in reverse positions in the circuit of a Thomson's Reflecting 

 Galvanometer. 



1920. Vinot's Sideroscope. J. and A. Molten^ Paris. 



1921. Apparatus, constructed by Professor Kaiser, for deter- 

 mining the absolute value of personal errors in observations on 

 the transit of stars. 



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

 tory, Leyden. 



The moment of the transit is registered by the action of a current. The 

 construction of this instrument dates from 1858 ; the first observations were 

 taken in 1859. (Dutch Records, Tome I., p. 193.) 



1922. Observing Seat for Reflecting Telescopes, in- 

 vented by the contributor. E. B. Knobel. 



The observer sits as on horseback, and by simply raising himself off" the 

 seat, standing on the ground or on the movable footrests, as if in his stirrups, 

 he can easily pull the seat up under him, and adjust it to the required height, 

 without dismounting or moving from the eye-piece of the telescope. Releasing 

 the ratchet wheel allows the seat to be lowered to any position. 



1922b. Fittings for Astronomical Telescopes. 



M, Lutz, Paris. 



1855a. Perfect Diagonal Planes (2), 3| in. across the 

 minor axis, for reflecting telescopes. Adam Hilger. 



1855b. Right- Angle Prisms (9), for total reflection. 



Adam Hilger. 



1923. Cooke's Lamp for illuminating the micrometric spider 

 webs of astronomical telescopes. A. A. Pearson, Leeds. 



The lamp is inserted in the brass body of the instrument, where it is held 

 by two projecting catches. The light, after passing through a condensing lens, 

 is received by a rectangular prism placed at such an angle that the beam is 

 totally reflected downwards into the window of the telescope, where its inten- 

 sity and colour are modified by diaphragms. The lamp is suspended on a 

 pivot, and also the framing and prism-box revolve from the bottom of the 

 supporting pillar, so that it has a universal motion accommodating it to the 

 position of the telescope. The weight of the end counterpoises the lamp, and 



