2 THE ART OF PROJECTING. 



the devices for giving proper movements to the mirror. 

 Their cost is from ten to twenty dollars according to 

 their size, workmanship, and attachments. On the 

 opposite page are engravings of several such as are in 

 the market. It is recommended that one be purchased 

 at the outset, if it can be afforded, but as many who 

 would be glad to work with one may not be able to 

 purchase it, directions will be given for making one that 

 will enable any person who is familiar with the use of 

 carpenters' tools to make one at a trifling cost that will 

 answer for many purposes. 



The room in which the porte lumiere is to be used 

 must, of course, be one into which the sun can shine. 

 A room having windows only upon the North side, 

 evidently cannot be used at all for such a purpose ; one 

 having windows only upon the East or upon the West 

 side could be used only in forenoon or afternoon ; while 

 one with windows looking to the South can be used 

 nearly all day. Choose then that window where the 

 sun is available the longest, and opposite to which can 

 be stretched the screen to receive the projections upon. 

 Next, take a well-seasoned piece of pine board a foot 

 or more in width, and an inch thick when dressed ; 

 cut it to the length of the width of the window sash, 

 so that it may fit into the window frame, and the sash 

 be brought down upon it ; this will keep it tightly in 

 place. With the compasses, scratch two concentric 

 circles in the middle of the board, one with a radius of 

 four inches, the other with a radius of four inches and 

 a half. Saw out the inner circle completely, and cut 

 the other but one half through the board, and then cut 

 away, making a square rabbet, as shown at b b. Next, 

 take a round piece of inch board of the same diametei 



