314 ©Frees. 



the rays of the pencil a be, flowing from the upper 

 extremity of the object A B, and passing through 

 the convex glass C D, to the plane mirror E F, 

 will be reflected from the mirror, and meet at I, 

 where they will form the extremity I of the image 

 I K, similar to the extremity A, of the object A B. 

 The like is to be understood of the pencil q r s, 

 flowing from the lower extremity of the object 

 A B, and meeting at K (after reflection from the 

 plane mirror), forming the extremity K of the 

 image, similar to the extremity B of the object ; 

 and so of all the pencils that flow from the inter- 

 mediate points of the object to the mirror through 

 the convex glass. This may be further improved, 

 by placing a convex lens of six inches focal dis- 

 tance, and four inches diameter, or more, if it be 

 required longer, between the mirror and the ground 

 glass; and though this will reduce the picture, yet 

 it will be more illuminated, and afford a pleasanter 

 view. 



Portable cameras are made, in which the objects 

 are represented upon a paper laid flat, which is 

 much more convenient for drawing. The sides of 

 the box are made to fold and shut up like a book. 

 To view the picture, the face is applied to an 

 opening made for that purpose ; and for tracing, 

 the hand is put through a cloth sleeve, fastened to 

 another opening. A mahogany framed head with 

 mirror and lenses, suitable to the distance from 

 about six to nine feet, is sometimes made to be 

 applied to the roof of a house commanding an ex- 

 tensive prospect : the head being contrived to turn 

 round in a horizontal direction. This instrument 

 can, by any intelligent carpenter, be easily applied 

 to the roof, to be put in and taken out occasionally. 

 A round table, of about three feet in diameter, 



