28 



Popular Science Monthly 



is automatically closed when the left 

 pictures appear on the screen, and 

 the left eye-aperture is closed when 

 the right pictures are being pro- 

 jected. 



The inventor operates the shut- 

 ters of the viewing disk electrically 

 to accord with the alternate projec- 

 tion on the screen of the right and 

 left hand films. 



Eachspectator carries a view- 

 ing disk which has two eye- 

 apertures operating alternately 



Giving Body Relief to 

 Motion Pictures 



THINGS about us seem 

 solid because each eye 

 sees from a slightly different point of 

 view. This can easily be tested by 

 looking through a window. Close first 

 one eye and then the other, and the window 

 framing crosses the view at entirely differ- 

 ent points. 



What really happens is that each eye 

 looks "around" rather more of one side 

 of an object than the other eye; and it is 

 the combination of the two impressions on 

 the brain that gives us the final impression 

 of solidity or body. 



In a system of projection for motion 

 pictures recently patented by M. F. Sulli- 

 van, this principle is applied so as to give 

 an effect of reality or solidity to the film 

 projected on the screen. 



By using two films which give the point 

 of view from each eye and projecting 

 pictures from each film strip alternately on 

 the screen, the impression of solidity is 

 attained, since it is only necessary to allow 

 that eye to view the screen when its cor- 

 responding film picture is being projected 

 thereon. 



Each spectator, however, must carry a 

 viewing disk with two eye-apertures. This 

 is necessary so that the right eye-aperture 



A Sheltered Feeding Table 



for the Birds 

 IRD lovers will welcome a new 

 idea in the construction of a 

 bird -feeding table operated on the 

 weather-vane principle. The 

 device is made of white pine 

 with a copper roof and is 

 pivotally mounted on an 

 eight-foot pole, so that it 

 turns with the wind. In 

 this way it is sheltered from 

 storms, and the birds have 

 a dry resting place and dry 

 food, whatever the weather. 

 An automatic hopper for 

 grain is provided so that 

 there is no waste. A wire 

 feed-rack and hooks for suet are 

 also arranged inside of the shelter. 

 Two arms at the sides furnish 

 perches for the birds and also aid 

 in the swing of the feed-table. 

 This arrangement answers the additional 

 purpose of a weather vane. 



The little house illustrated on the right 

 below has a sheltered feeding table under- 

 neath it and below that is a still smaller one. 

 The house is commodious and attractive and 

 will furnish housing for a number of birds. 



HANDLE 



The feeding table veers with 

 the wind and is therefore 

 useful as a weather vane 



