302 



Popular Science Monthly 



of triangles at an angle of 120 deg. The 

 center row of triangles should be bent at 

 an angle of 72 deg. The bending may be 

 done by means of a "brake," or over a 

 "hatchet stake" with a mallet. 



The beginner, learning the trade, will 

 be interested to know the scientific name 

 for such a finial. In solid geometry it is 

 one of a group of forms called "poly- 

 hedrons," meaning many sided solids. 

 The word "poly" means many. A cube is 

 a polyhedron that has six equal faces and 

 its special name is a "hexahedron." A 

 solid with eight faces is an "octahedron." 

 This finial, the pattern of which is de- 

 veloped, is called an "icosahedron," because 

 it has twenty faces. 



Folding Camp Fireplace Made of 

 Angle Iron 



ANY one who likes to go camping will 

 l be interested in these stoves. The 

 only tools needed to make them are a 

 hacksaw, riveting hammer and a breast 

 drill with a 3/16-in. bit. The sides are 

 made of two pieces of angle iron % by 

 Y% in. The ones used in making the fire- 

 place illustrated were taken from an old 

 bedstead. The legs are % by 3/16-in. 

 flat iron and the bars across the top are 

 from flat galvanized steel 1 by 3/16 in. 

 This is used to hold the sheets of gal- 

 vanized iron together. These sheets may 

 be obtained at any tinsmith's shop at a 

 small price. One advantage of this style 



a. A 6 



ANGLE IRON- 



LEGS FOLD UP 

 WHEN NOT IN U5E 



The frame may be easily folded flat so 

 that it can be put away in a narrow place 



of grid or fireplace is that it folds up com- 

 pactly and is steady when set up. It also 

 has the great advantage of being adjust- 



able as to width. The fireplace folds into 

 a narrower but longer space than when 

 open. I have found it extremely useful 

 as a stand for an ordinary camp stove 

 when used in a tent; for when it is opened 

 to its full extent it just fits a small iron 

 stove. — B. E. Dobree. 



Garden Seat with Checkerboard 

 in Its Top 



GARDEN seats of the ordinary bench 

 type can be made to serve a twofold 

 duty by placing in the center of their upper 

 surfaces a checkerboard design. In the 



The checkerboard on the garden seat 

 makes checkers an inviting outdoor game 



wood top, squares may be cut out with a 

 chisel or knife and alternate ones painted 

 black. The checkermen can be kept in a 

 small drawer placed under the seat. 



If a cement seat is made along these lines, 

 black and white square tiles can be set in 

 the cement to form the checkerboard 

 design. In making the seat of cement, 

 places must be provided for screws or ex- 

 panding bolts which must be inserted on 

 the underside at the center for holding the 

 drawer slides. — Edward R. Smith. 



Constituency of Rubber for Side 

 Walls of a Tire 



THE side walls of a tire must be flexible 

 in order to properly distribute the 

 strains, give resiliency, minimize heat, 

 prevent sharp bending of the fabric,, break- 

 ing and separation. Therefore, it is desir- 

 able that the rubber on side walls of a tire 

 be elastic and not too dense or firm; the 

 kind of hard wear resisting rubber used on 

 the tread is not suitable for covering the 

 side walls. The difference in materials and 

 adaptability for tires may be compared 

 with automobile and machinery parts- 

 some materials are required to possess great 

 strength and some are selected for other 

 qualities, according to their tasks. 



