IX. EDUCATIONAL. 429 



1890a. Earth and Sun Instrument. 



Horatio Allen, Homewood, South Orange, New Jersey ', 



U.S.A. 



This instrument presents clearly 



1st. The relations of the earth to the sun. 



2nd. The relations of the surface of the earth in any parallel of latitude, 

 in all positions of rotation, and at all places of the earth in its orbit, to lines 

 of light and heat from the sun. 



1891. Apparatus intended to elucidate the Apparent Mo- 

 tions of Planets seen from the earth. 



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

 tory, Leyden. 



The apparent motions of a superior planet are depicted on the inner surface 

 of a cylinder. This apparatus was made by Professor Kaiser for his popular 

 lessons on astronomy. 



1892. Apparatus for demonstrating the Path of the Moon 



round the Sun, as an epicycloid, without cusp or loop. 



Dr. Charles Oppel, Frankfort-on-the- Maine. 



When the handle is turned the moon will mark, by means of a pencil, to 

 be inserted in the socket under it, its serpentine path on a sheet of paper 

 laid underneath. 



1892a. Solarium, a mechanism for Kinematic demonstration 

 of the real orbits in the solar or the terrestrial system. 



Royal Academy of Industry, Berlin, Director, Prof. T. 

 Reulcaux. 



In ascertaining the polar orbs (centroids) for the rotation of the earth 

 about the sun, an ellipse is obtained in one focus of which the sun is 

 situated. The polar orb of the earth is a circle, and the latter travels on the 

 ellipse. The curves actually described by the earth are roulettes of this 

 system. The mechanism is arranged for Kinematic adjustment, so that on the 

 one hand the roulettes of the earth in the solar system, and on the other those 

 of the sun in the terrestrial system, can be demonstrated. 



1893. Model of the Paths of the Earth and of Venus, 



with movable balls on a stand, for demonstrating the position of 

 the nodes and apses, inclination of the orbit, the period of Venus, 

 culminations, &c. J. J. Oppel. 



1894. Armillary Sphere of brass, to take to pieces, with 

 horizon and azimuth, meridian, equator, ecliptic, tropics, and 

 polar circles, movable sun, &c. J. J. Oppel. 



This sphere demonstrates many of the definitions of spherical astronomy : 

 zenith, altitude, and azimuth culmination, circumpolar stars, right ascension: 

 and declination, longitude and latitude, the seasons, hour-angles, sunrise and 

 sunset according to time and place, length of the day, &c., &c. 



1895. Apparatus for demonstrating (a) Foucault's Pen- 

 dulum Experiment, and (b) the relation between the Period 

 of Revolution of the Pendulum and Geographical Lati- 

 tude. J. J. Oppel. 



