REOREAT1S 



< of card, in which U a small hole, made by means of a 

 needle, to which the eye in applied. Wo shall here suppose the 

 glass to be plain on one aide, and on tho other to oonsirt of nix 

 rlium! . placed around tho centre, and of nix triangular 



, hi.'h occupy tho ronm. 



hexagon. When everything 

 is tlniri prepared, fix the HU 



it a cortain distance from 

 t ho picture, according 



i IITO desirous that the part* 

 to bo delineated should bo nearer 



i.uth.T from each other, 

 lint this distance ought at least to 

 ! four times tin- diameter of tba 

 s|ihiTu on which tho polyhedron 

 of the gloss could be inscribed, 

 nud tho distance from tho eye to 

 : iss may bo equal to twice 

 that diameter. Then place the eyo 

 at tho hole K, the distance of 

 whii-li has been thus determined, 

 and with a stick having a pencil 

 at the cud of it, if the hand can- -', 

 not roach the pasteboard, trace ^ 

 out in aa light a manner as pos- 

 sible the outline of tho space . 

 observed through one facet, and 9 

 do the same thing in regard to * 

 the rest. This operation will 

 require a great deal of accuracy 

 and patience ; for to render the 

 work perfect, no perceptible inter- 

 val must bo left between the two spaces seen through two 

 contiguous facets it will bo better, on tho whole, if they rather 

 encroach a little on each other. 



Care must also bo taken to mark each space with the same 



to delineate the regular picture iateaded to be eeeo, and to 

 transpose it into the spaces when it appears distorted. Ao. 

 cording to mathematical accuracy, it would be neoeeeary for this 

 purpose to form a projection of the glass eat into faaeai, sap- 

 posing the eye at the distance at 

 which it is really placed; bat M 

 p: we suppose it a little more re- 



note, we may, without any aene 

 error, assume M the field of the 

 regular picture the vertual pro- 

 jectkm as seen in Fig- *, wbere it 

 ie repreeented such ae it would 

 appear to the eye placed perpen- 

 dicularly above its oeatre and at 

 a very conaiderable distance. 



Delineate in the field, which in 

 this caee will be hexagonal and 

 compoeed of six rhomhokU and 

 u triangles, any fiffnre whatever 

 ae a portrait for trample, eixl 

 then, considering that the epaoe 

 abed (Fig. 5) is that where too 

 portion of the picture marked 1 

 ought to appear, it mart be 

 ferred thither with ae much < 

 ae poeeible ; do the eame thing in 

 regard to the rest, and by theee 

 mean* the principal part of th 

 picture will be completed ; but ae 

 it is intended to enow *rm^btng 

 else Decide what ought to be seen, 

 it must be dieguieed by mean* of 



some other objects painted in the remaining part of the field, 

 making them to harmonise with those already painted, ao that 

 the whole shall appear to form one regular subject. All thie 

 must, however, depend upon the tasto and genius of the artist. 



number as that assigned to each facet, in order that they 

 may bo again known. This, however, will be easy by observing 

 that the space corresponding to each facet is always trans- 

 ferred parallel to itself from top to bottom or from right to 

 left, on the other side of the centre. The next thing is 



DISSOLVING VTEW8. 



Of all the contrivances in which the laws of refraction are 

 employed, none can surpass in usefulness and beauty the appara- 

 tus used to produce the dissolving views. Ae an educational 

 machine it is certainly valuable, aa there u hardly a subject 



