UNIVERSAL REFLECTING ILLUMINATOR. 2 1 '.» 



was gained nearly half a century back in polishing the specula 

 for a Newtonian telescope ; but I am not aware that any better 

 method has since been devised, and, therefore, as this has fully 

 answered the purpose, is very simple and easily put in practice, it 

 may be followed with advantage. Having obtained the silver plate, 

 and had it soft-soldered to a brass back and cut to the size, let a 

 piece of sealing-wax or a small block of thick plate glass be attached 

 to its back as a handle and to prevent flexure. Now procure a common 

 writing-slate with a flat and smooth surface, and grind the silver 

 with water until all scratches have disappeared, and a level face has 

 been produced. If the surface be now well burnished with a straight 

 burnisher it will add greatly to the brilliancy and durability of the 

 polish. Next, take two pieces of thick plate glass, not less than 

 three or four inches square, and upon the surface of one melt 

 some pieces of clean pitch until soft enough to be spread evenly 

 with a hot knife to about the thickness of a sixpence. Let the 

 surface of the other glass be smeared with soap and water, and then 

 pressed upon the soft pitch until the latter shall have acquired a 

 flat and highly polished surface, when it may be slid off, and the 

 pitch left to harden . 



Obtain at the chemist's a pennyworth of " precipitated car- 

 bonate of iron" (the softest and finest "rouge" possible), and 

 mix with a few drops of water to the consistence of cream, and 

 let the metal be lightly worked with this over all parts of the 

 pitch in small circles, carefully avoiding all dirt or grit until the 

 polish, commencing in the centre, shall have spread to the edges, 

 and having a deep and brilliant lustre that will reflect objects with 

 the utmost sharpness of definition. Any future " refreshing" will 

 be best done with the tip of the finger, slightly breathed upon and 

 then dipped in the dry powder, and, very gently, with a small circular 

 motion, the whole surface gone over by degrees. from one side to the 

 other. 



Description of Plate XIX. (Lower Part). v 



Fig. 1. A side view of lamp, lens, and reflector, deflecting the light from 

 A to B. 



,, 2. Indicates the different positions of reflector required for obtaining 

 different angles of illumination. 



