104 



Popular Science Monthly 



of the negatives. That is, a positive 

 from the green plate will show the leaves 

 transparent, and the rose dense; while 

 that from the "red" plate will show the 

 leaves dense, and the rose transparent. 

 Dyes used in this process affect only 

 the dense places. It is obvious that 

 if you want a red rose to be red in 

 the resultant picture, you will have to 

 color the positive from the "green" 

 negative red, that being the only one 

 showing the red rose as a dense area. 

 Similarly, you will have to color the 

 positive from the green negative "red," 

 since in this case the leaves are dense. 

 After dyeing them in this manner, the 

 plates pass through a special process to 

 eliminate the opaque black silver on the 

 plates, leaving only the colored images. 

 This process completed, the two plates 

 are placed face to face and registered 



properly. Then you see the red rose 

 in its proper place among the green 

 leaves. 



The next step is to cement these two 

 positive emulsions together. This done, 

 they are stripped from the glass and 

 transferred to paper, canvas, ivory (in 

 the case of a miniature), or any other 

 backing. In their new positions they 

 look not unlike an oil painting, especially 

 when canvas is used as a mount. 



For the sake of simplicity, the fore- 

 going description of the red rose and 

 green background referred only to these 

 two colors. It is understood of course 

 that almost any color which may have 

 been present in the original object also 

 appears in the finished picture. This is 

 possible because red and green combined 

 in different proportions by the process 

 here used will give such desired colors. 



How a Steamer's Engine-Room Is Ventilated 



FRESH AIR 

 DUCT- 



PHYSIOLOGISTS have shown in re- 

 cent years that the chief effect of 

 ventilation and open air treatment de- 

 pends on the movement, temperature 

 and moisture of the air, and less upon its 

 chemical properties than was expected. 

 For this reason the cooling of overheated 

 engine-rooms, underground or underdeck, 

 is best obtained, as engineers have dis- 

 coN'ered, by flood- 

 ing them with fresh 

 air from outside 

 under slight press- 

 ure. This positive 

 ventilation or a 

 continuous change 

 of air also removes 

 a\\ noxious gases 

 anfl smells emanat- 

 ing from the oil and 

 bilges. 



The accompany- 

 ing driiwing shows 

 a transverse sec- 

 tional view of the 

 engine-room of the 

 "Aquitania," with 

 the recommended 

 method for flood- 

 ing the confined 

 space with cool, 

 fresh air under 

 moderate pressure. 

 The air is delivered 



OPEN MAIN 

 HATCH 



'^m^ 



ENGINE ROOM 



A cross-seclion view of the "Aquitania,' 

 showing ventilating arrangement 



into the engine-room by a large open fan 

 placed at the junction of the lower ends 

 of the air-shafts, so that the full volume 

 of fresh air, equal in this instance to 

 about one hundred and fifty thousand 

 cubic feet per minute, is propelled into 

 and properly distributed through the en- 

 gine-room without lossfromdeliveryducts. 

 When desirable, the air in the engine- 

 room may be 

 changed one hun- 

 dred and twenty 

 times an hourwith- 

 out uncomfortable 

 drafts. The cool air 

 is drawn, not forc- 

 ed, down from the 

 ujipcr deck and 

 delivered laterally 

 by open fans jilaccd 

 low down in the 

 engine-room so as 

 to Hood the whole 

 space with air, the 

 cooler incoming air 

 falling towards the 

 tliior, displacing 

 the heated air and 

 exjielling it up the 

 main hatcli. Many 

 transatlantic liners 

 have the \enlilat- 

 ing system illus- 

 trated. 



STEAM TURBINE 



