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XVII. Description of Mr. Ez. Walker's new Optical 

 Machine called the Phantasmascope, 



To Mr. Tilloch. 



A SIR, 

 MONG the various amusements that the sciences afford 

 us, none are more wonderful than those which we derive 

 from optics. This science teaches us to distrust the evi- 

 dence of our senses ; for when we use optic glasses, instead 

 of viewing real objects, we generally see nothing but phan- 

 toms. 



The new optical machine, of which I now take the liberty 

 to send you an account, is constructed to afford entertain- 

 ment to those who derive pleasure from optical illusions. 

 A person standing before this machine, sees a door opened ; 

 a phantom makes its appearance, coming towards him, and 

 increasing in magnitude as it approaches. When it has ad- 

 vanced about three feet it appears of the greatest magnitude, 

 but as it returns it becomes gradually contracted in its di- 

 mensions until it re-enters the machine; when it totally 

 vanishes. This phantom appears in the air like a beautiful 

 painting, and in such rich brilliancy of colouring, that it is 

 by no means necessary to make the room dark ; for, on the 

 contrary, this aerial picture is seen rather in greater perfec- 

 tion when it is illuminated. 



This machine, which may be called the phantasmascope, 

 from the effects which it produces, is constructed in the fol- 

 lowing manner : 



Plate III. represents a section of this machine. 



A BCD, a wooden box, 36 inches by 21, and 22 deep. 



EF, a concave mirror, 13 inches diameter, placed near 

 the end BD. 



A C, the other end, is divided into two parts at m by an 

 horizontal bar, of which m is a section. 



Am, a door that opens to the left hand. 



710, a board with a circular opening, 10 inches diameter, 

 covered with plate glass on that side next the mirror. 



Vol. 27. No. I0(j. March 1807. G GHI, 



