744 



Popular Science Monthly 



which makes it possible to use the in- 

 vention as a roof-ladder, or in place of a 

 trestle without extra braces to prevent 

 the spreading of the ladder at the bottom. 

 The ladder may be used either as an ordi- 

 nary extension ladder or as a step-ladder 

 and its rigidity enables it to stand the 

 most severe tests. 



This ladder will not slip, buckle or collapse 



A Safe Ladder Appears. You 

 Can't Break Its Rungs 



CHARLES J. BROWN, of River Falls, 

 Wis., is the inventor of a new ladder 

 which combines many advantages and 

 novel features. 

 His ladder is light 

 yet strong, and its 

 rungs, which are of 

 metal, are so fast- 

 ened to the wood- 

 en rails of the lad- 

 der, that the struc- 

 ture becomes per- 

 fectly rigid. 



The rungs have 

 a flat tread which 

 prevents the foot 

 from slipping. 

 Safety devices are 

 provided, which 

 prevent the slip- 

 ping of the lower 

 end of the ladder 

 on smooth or un- 

 even ground, and 

 the slipping side- 

 ways of the upper }^''^. '"^^'^j^s 



J rni • \ IS Simplified 



end. There IS also by this recent 



a locking device, invention 



Chemicals and Machines Supplant 

 Men In This War 



THIS is the most scientific war ever 

 fought. There is less dependence 

 on man-power and more on machinery 

 than at any time in the history of the 

 world. We pin our faith to high explo- 

 sives, poison gases, tear shells, gas masks, 

 liquid fire, etc., all of which are applied 

 chemistry, and to machine guns, heavy 

 artillery, automobiles, submarines, air- 

 planes, and so forth, which are very much 

 refined mechanics. The greatest minds 

 in the scientific and mechanical world 

 have pooled their brains and obtained 

 wonderful results. 



Place-Finding on Maps Is Made 

 Easy by New Device 



THE system of using index letters and 

 numbers to enable one to find any 

 spot on a map by referring to an in- 

 dex has been am- 

 plified by a device 

 primarily designed 

 for wall-maps, but 

 could doubtless be 

 adapted to smaller 

 ones too. A rod 

 slides along the top 

 edge of the map and 

 carries a movable 

 indicator. The in- 

 dicator is first ad- 

 justed to the prop- 

 er place on the 

 side index, and 

 then the rod is 

 moved along until 

 it coincides with 

 the correct letter 

 or figure on the 

 top index. The 

 indicator then 

 automatically 

 points to the de- 

 sired place. 



