ASTRONOMICAL SLIDERS. 



sliders. It is obvious also that the fossil animals could be very 

 advantageously presented in this way. 



14. But of all the departments of instruction for young persons, 

 that to which the magic lantern lends itself most happily is 

 astronomy ; and here the artists have already prepared admirable 

 sets of sliders, which can be obtained at moderate prices, and 

 convey, in a most pleasing manner, most important instruction.. 

 Thus, the annual and diurnal motion of the earth, with the 

 vicissitudes of day and night, and the succession of the seasons, 

 are executed by means of a slider provided with mechanical 

 expedients for producing the several effects. In the same 

 manner, sliders are adapted to show the effects of the sun and 

 moon in producing the tides of the ocean ; the motions of the 

 planets round the sun ; solar and lunar eclipses ; the motions of 

 comets, with the development of their tails, and in a word all the 

 principal motions of the bodies composing the solar system. 



15. A class of astronomical objects, which would supply highly 

 interesting and instructive subjects of optical exhibition with 

 the lantern, would be telescopic views of the sun, moon, and 

 planets. The spots on the sun well delineated, as they might be, 

 the remarkable lineaments of the moon, showing so conspicuously 

 the inequalities of its surface, the peculiar appearances exhibited 

 by the disc of Mars, on which the polar snow is visible, and the 

 outlines of land and water faintly apparent, the atmospheres of 

 Jupiter and Saturn, stratified by their atmospheric currents, so 

 as to produce belts, the triple ring of Saturn, the motions of the 

 satellites of Jupiter and Saturn, showing their eclipses, are 

 severally phenomena which might easily be exhibited with the 

 lantern. Some of these have been already attempted by the 

 opticians, but in a manner that had better have been left alone. 

 The telescopic views of the planets given upon the common 

 sliders are worse than worthless, since they produce most 

 erroneous notions. The view of the moon usually given is less 

 objectionable ; nevertheless, nothing would be more easy than to 

 get proper sliders painted from good originals, which are easily 

 obtained. Excellent telescopic views of Mars, Jupiter, and 

 Saturn have been reproduced in my work on astronomy from the 

 original drawings of Madler, Herschel, and other authorities. I 

 have given them on a scale such that they could be transferred to 

 sliders without difficulty ; Saturn with his rings I have also 

 given from the original drawings of the most recent observers. 



Yarious views might be given of different parts of the moon's 

 surface, and of the solar spots ; these I have also given on 

 a proper scale from the originals of Pastorff, Madler, Herschel, 

 and others. Comets, with their extraordinary changes of form 



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