168 



THE POPULAR EDUCATOR. 



RECREATIVE SCIENCE. XVIII. 



THE ASTBOMETBOSCOPE THE THAUMATBOPE THE 

 PEDEMASCOPE. 



IN the last paper the principle of the astrometroscope, an in- 

 strument for producing elaborate patterns by the movement of 

 star-like figures, was alluded to and illustrated by Pilkington's 

 simple contrivance. The appa- 

 ratus called the astrometroscope 

 was devised and constructed by 

 Mr. Pichler, and consists of a 

 metallic plate, in which a number 

 of perforations in the form of 

 stars at equal distances from 

 each other are made, like a wall- 

 paper with stars on it ; and when 

 ' fitted into the lantern and ex- 

 hibited by the oxy-hydrogen 

 light, white stars are apparent 

 on a black ground, or that part 

 of the disc which is not illumi- 

 nated. The first effect is pro- 

 duced by quickly moving the 

 perforated star-plate diagonally, 

 when each point of light or star- 

 like figure leaves a track of light, 

 similar to a meteor, and the effect 

 on the disc is that of a number 

 of diagonal lines moving rapidly, 

 every line or track of light being 

 perfectly distinguishable the one 

 from the other. The next change 

 is effected by imparting a general 

 circular motion, and if the star 

 figures were subjected only to 



this movement they would merge one into the other, there 

 would appear so many circles of light and dark bands, and no 

 other result could be obtained. 



In this apparatus the movements are different, and the ope- 

 rator can at pleasure impart 

 either a diagonal, circular, per- 

 pendicular, or horizontal motion, 

 cr a combination of them all. 

 Thus a multiplication of well- 

 known forms can be projected 

 on the disc, such as straight 

 lines, then the same lines thrown 

 into waves, next into parabolic 

 curves, circles with star-like 

 figures in the central portions 

 (shown in Fig. 1), elliptical 

 figures, or oblate spheroids. 



Just as the kaleidoscope, with 

 constant movement, may pro- 

 duce by reflection an endless 

 variety of figures, so the astro- 

 metroscope, on a different prin- 

 ciple viz., by the formation of 

 tracks of light left upon the 

 vision after a variety of compli- 

 cated movements of points of 

 light forms an endless series 

 of line patterns. The observer 

 is reminded of those beautiful 

 geometrical figures obtainable 

 by the slide-rest and overhead 

 motion attached to the most 

 expensive lathes. 



A large book might be devoted to the illustration of the 

 various designs obtainable from the astrometroscope; space 

 alone must limit the drawings of these figures to one more 

 example (Fig. 2). This pattern looks like a piece of crochet- 

 work, the crossed loops in the circles and portions of circles in 

 the oval figures being very curious, and only equalled by other 

 effects, in which the lines appear like shelves or thin boards, 

 one above the other, each shelf having so many circles upon it, 

 and moving half round horizontally and returning again to its 

 former position, as if the shelves were on pivots ; or the lines 







become perpendicular, and perform the same curious motion at 

 right angles to the former ones. In fact, it takes a quarter of 

 an hour to show all the figures obtainable, even when the ope- 

 rator makes the changes as rapidly as possible, consistent with 

 the separate exhibition of each pattern. Indeed, we might say 

 with Pope, in showing how cleverly art, in the astrometroscope, 



may imitate Nature's meteors > .,, , T , 



All Nature is but art unknown 



to thee ; 

 All chance, direction which thou 



canst not see ; 

 All discord, harmony not undet 



stood; 

 All partial evil, universal good." 



A learned physician, Dr. Paris, 

 appears to have been the first 

 who specially directed attention 

 to those more amusing effects in 

 which we seem to be able to look 

 through an opaque substance and 

 see both sides of a piece of board 

 or card upon which different 

 designs are painted. He wrote a 

 little book on " popular science," 

 to which he gave the happy title 

 of " Philosophy in Sport made 

 Science in Earnest." It is 

 written in the dialogue style, and 

 is somewhat pedantic, for the 

 worthy doctor will trot out his 

 classics, as much as to say, 

 "Don't think I wish to put the 

 learning of science before the- 

 acquisition of Latin and Greek." 



Fig. 1. At page 376, he thus introduces 



what he calls his new inven- 

 tion, forgetting that from time immemorial children had twirled 

 round coins and seen both sides at the same time. But let Dr. 

 Paris speak for himself. His preface runs thus : " A new 

 Optical Toy, invented by the Author, and termed the Thauma- 

 trope Explanation of its Prin- 

 ciple Retentive Power of 

 lietina " : 



Tom's holidays were now draw- 

 ing to a close, and the children 

 were summoned into the library to 

 receive their last lesson in philo- 

 sophy. 



" You have lately witnessed an 

 experiment," said Mr. Seymour, 

 " which must have convinced you 

 how liable the ear is to be deluded 

 with respect to the nature and 

 direction of sound; I shall now 

 show yon that the eye has also its 

 sources of fallacy." 



" If you proceed in this manner 

 you will make us Cartesians,"* 

 exclaimed the Vicar. 



" I shall illustrate my subject by 

 means of a toy which I have lately 

 invented," said Mr. Seymour ; 

 " and, unless I am much mistaken, 

 it will afford as much amusement 

 to the elder as to the younger 

 members of our party, although 

 the Vicar may perhaps regard it aa 

 a more hostile instrument than 

 even that of the wooden horse 

 which filled unhappy Troy with an. 



fig. 2. armed onemy. It is a small 



machine," continued Mr. Seymour, 



" which is well calculated to furnish us with some capital puns and 

 well-pointed epigrams." 



" With puns ! " exclaimed the horrified Vicar, who no sooner heard 

 this appalling declaration than, like another Laocoon, he deprecated 

 the introduction of the donum exitiale (hurtful gift) within the walls 

 of Overton Lodge. But his hostility was soon disarmed, not by the 



* The Cartesians maintained that the senses were the great sources 

 of deception ; that everything with which they present us ought to 

 be suspected as false, or at least dubious, until our reason has con- 

 firmed the report. 



