146 



Popular Science Monthly 



A Coating Which Gives the Appearance 

 of Stone to Wood 



TO make imitation stone for outdoor 

 furniture, sun-dials, flower pots, etc., 

 the following can be used: 



10 parts lime 

 12 parts rosin 

 I part linseed oil 



Dissolve ingredients thoroughly and ap- 

 ply the mixture while hot to the wood as a 

 coating. The result will be an attrac- 

 tive stone-like appearance that will last 

 indefinitely. — L. E. Fetter. 



A Special Ladder for Use in 

 Boiler Shops 



THE type of ladder illustrated is 

 especially made for use in boiler and 

 car shops where it is necessary to climb up 

 to moderate heights for doing work. Being 

 of the A-type it can be used like a painter's 

 ladder and a plank can be put between two 

 of them to form a trestle which will ac- 

 commodate more than one workman. This 

 method of construction makes the best pos- 

 sible ladder — strong, safe and economical. 

 It is built of short pieces of i3^-in. pipe, 

 each about 21 ]/% in. long, which may be 

 picked up about any shop where con- 

 siderable pipe is used, such short pieces 

 being useless for general work. 



% XI BRAS5 

 TEES 



V&BOLT THROUGH, 

 £ RUNGS RIVETED 

 %VER AT NUT 



An A-shaped ladder made of short lengths 

 of gas pipe and fittings for a boiler shop 



The pipes forming the rungs are 1 in. 

 in diameter. In the making of the ladders 

 illustrated, sixteen 1% in. by 1 in., brass tees 

 and eight %-in. bolts, one for each rung, 



were used in each ladder. The parts were 

 hinged at the top and pointed irons were 

 fitted in the lower ends as shown. A chain is 

 used between the parts to keep them from 

 spreading. 



While this ladder is very heavy, yet for 

 the usage to which it will be subjected the 

 construction is most desirable and at the 

 same time inexpensive. — Joseph K. Long. 



Three Plates and Three Color Screens 

 Used in New Color Photography 



IN a recent patent on color photography 

 there is brought out a process whereby 

 three sensitive plates are placed together 

 in such a way that the color screens in 

 in them produce the desired effect on the 

 plate. 



Tn nhtain OPAQUE BACK SCREEN. 



10 o Drain carrier class 



these results it red-sensitive coatin&| 

 is necessary to 

 have all plates red color-screen- 

 that are used ^-se nsitive coati 

 in sets, sensi- 

 tized at the 



same time so yellow color-screen 

 bame urae, bo blue-sensitive coating 

 that they will 

 age the same 

 and have the 

 same emulsion. 



carrier GLASS - 



Arrangement of plates in 

 pack to record natural colors 



The ordinary dry plate is sensitive to the 

 blue rays. In making up the sets green- 

 sensitive plates must be used, which are 

 sensitized with a chemical dye. A batch of 

 these plates is divided into two parts, the 

 first portion being coated on the back with 

 opaque substance and allowed to dry, after 

 which they are treated for rendering them 

 red-sensitive. In the meantime, the second 

 portion of the plates, which are already 

 green-sensitive, are superficially coated 

 with a temporary green. Then they are 

 assembled to form a plate pack, and if 

 desired, a blue-sensitive is combined with 

 them. By securing these together they 

 make a unit which may be exposed in any 

 desired manner. After exposure the plates 

 are separated, developed and fixed. 



The chemical dye which gives a plate 

 sensitiveness for a given color may be 

 termed a color-sensitized agent and the 

 plate a dye-sensitized plate. The green- 

 sensitizing agent is preferably included in 

 the original emulsion. The illustration 

 shows the sensitive plates and their arrange- 

 ment in a pack to record the natural colors 

 as the rays fall, upon them successively 

 from the camera-lens. 



