2Q6 



Popular Science Monthly 



direction. If we look at the earth 

 through a telescope, however, we limit 

 our field of vision to a comparatively 

 small area, which rushes past so rapidly 

 that we are unable to distinguish a 

 single object. The earth seems to "flow" 

 under us. 



If you have carefully followed the 

 foregoing explanations you will be quite 

 able to appreciate fully a drift indicator 

 which has recently been developed and 

 which is regarded' as one of the most im- 

 portant contributions to the science of 

 aviation. 



The lubber-line is engraved on a mov- 

 able ring mounted inside the compass 

 and encircling the compass card. A tele- 

 scope, provided with five fine cross-hairs, 

 is mounted at any convenient location 

 and so connected with the lubber-line 

 ring that any movement of the telescope 

 results in a corresponding movement of 

 the ring. 



When the aeroplane is flying as in- 

 dicated in Fig. 1, the positions of the 

 lubber-line, the compass card and the 

 cross-hairs of the telescope are as shown 

 in Fig. lA. Looking through the tele- 

 scope the earth appears to flow in the 

 direction of the wavy lines. We know 

 the aeroplane is drifting, and at once we 

 set the cross-hairs to parallel the lines of 



Dust from the mop falls through the sieve 

 and is caught in the dustpan 



drift; the lubber-line is automatically 

 and simultaneously moved in the same 

 direction and to the exact number of de- 

 grees. Fig. 2 shows the aeroplane fol- 

 lowing the course unchanged, but the 

 compass card Fig. 2A indicates our 

 course to be actually northwest and not 

 north. Fig. 3 and 3A show that the pilot 

 has swung his craft around to meet the 

 changed c jnditions. While the aeroplane 

 is heading northeast, the actual line of 

 flight is now due north. 



Battery Wax Recipes. 



THERE is nothing better for the 

 upper edges of glass cells or 

 open-circuit batteries than hot parafQn. 

 Brushed about the upper edge it pre- 

 vents the sal ammoniac or other fluids 

 from creeping up over the top. 



The paraffin can be colored, if neces- 

 sary, with red lead, green dust, or pow- 

 ders of various kinds. Generally the 

 paraffin is used without color, so that 

 it has a frosted appearance when cool. 



A black wax for stopping the tops of 

 dry cells and coating the tops of car- 

 bons is composed of tar and pitch in 

 equal parts. These are made into a pasty 

 mass with turpentine heated over a 

 stove, but not over an open flame be- 

 cause the ingredients are inflammable. 

 The compound should be like very thick 

 molasses, so that it can be worked with 

 an old knife. 



Another good black wax is composed 

 of paraffin, eight parts ; pitch, one part ; 

 lamp black, one part. Heat the mixture 

 and stir it until thoroughly mixed. Ap- 

 ply with a brush or dip the parts into 

 the warm liquid. 



Oil Mop Cleaner and Dustpan 



THE oil or polish mop is coming 

 into very general use in homes 

 with finished floors. The dust is 

 quickly picked up in the soft yarn mesh 

 of the mop but the problem of remov- 

 ing the dust from the mop then arises. 

 A special cleaner has been devised 

 which is also a dustpan. One holds it 

 in place with a foot upon the short han- 

 dle, and combs the mop back and forth 

 over a perforated platform, the dust 

 falling into the dustpan beneath. This 

 can be used in the house as well as out 

 of doors. 



