138 



Popular Science Monthly 



A Keyless Collapsible Letter 

 Box for Army Camps 



THE letter box shown below was origi- 

 nated by a mechanic in the Field 

 Artillery of the U. S. Army. The 

 upper part of the box consists of a 

 wood frame to admit the upper part of 



Flail slotx Tin cover 



Wooden 

 frame 



Letter box designed especially for use 

 in the army camp. It is portable 



a canvas bag. It is so constructed that 

 when the metal cover is raised the canvas 

 bag is released. Only army officers who 

 are authorized to do so make the 

 collections. The whole device can be 

 readily taken down and packed for 

 shipment. — Dudley Hess. 



state and then add enough water to make a 

 stifif paste. Apply it to the stove lining 

 where the repairs are required. The car- 

 borundum in this mixture helps the lining to 

 withstand the heat, since carborundum is an 

 artificial substance, made under intense heat 

 in an electric furnace. 



After the lining is applied to the stove, let 

 it dry for several days, if possible. When 

 starting a fire for the first time, let the fire 

 come to its maximum heat gradually. 

 After that, any kind of firing may be done, as 

 the lining, once having thoroughly dried, 

 will keep in good condition for an indefinite 

 time. — W. S. Standiford. 



How to Make a Good Lining for 

 Stove Fireplaces 



IRON fireboxes, whether made of cast or 

 wrought iron, usually deteriorate when 

 the fires are kept constantly going for any 

 length of time. To prevent this, the stove 

 manufacturers supply their stoves with fire- 

 places having firebrick linings. Even these 

 in time, due to the action of the heat, break 

 into pieces, thus exposing the iron to the 

 action of the heat. The following cement 

 will take the place of the brick satisfactorily 

 and it withstands heat. Take 6 parts of 

 potters clay, 2 parts of plaster of Paris or 

 cement if obtainable, 1 part of wood ashes, 

 and 3 parts of carborundum in powder 

 form. Mix all of the ingredients in the dry 



Homemade Copying Paper for 

 Manifold Work 



HOMEMADE copying paper, pre- 

 pared by rubbing one side of com- 

 mon scratch paper with a very soft lead 

 pencil, is more satisfactory for many pur- 

 poses than carbon paper. For transferring 

 map lines from field sheets to the office 

 map, copying drawings, sketches, etc., it 

 will be found very convenient. 



Lines traced on a map or drawing made 

 from such copying paper can be very 

 easily erased. The erasure of the usual 

 carbon-paper lines is not so readily 

 accomplished. — Peter J. M. Clute. 



Blowing a Pocket Gear From an 

 Automobile Transmission 



A POCKET gear on an automobile 

 transmission having a thrust button, 

 became cracked and it was necessary to 



remove it. 

 The crack 

 caused a burr 

 in the hole 

 that prevented 

 the removal 

 of the gear. 

 The only 

 method that 

 could be used 

 was the usual 

 one of explod- 

 ing powder 

 back of the pinion stud. A small hole 

 was drilled in the shaft to gain entrance 

 to the space back of this stud and into this 

 a quantity of powder was poured. The 

 powder was ignited with a fuse and the 

 pinion removed. — Geo. F. Weiher. 



Holding part in vise for 

 blowing out the pinion 



