Testing Farm Seeds. 347 



construction is clearly shown in figure 13, to which the letters used in 

 the following description refer: 



The balance consists of a hexagonal, or six-sided, pencil (a) notched 

 as nearly as possible in the center and halfway through the lead. Make 

 a rather wide V-shaped notch. Half of a similar pencil is notched like- 

 wise at its center, care being taken that the angle at the apex or "bot- 

 tom" of the notch is made narrow, straight and smooth. At this point 

 the balance rests on the small blade of a knife, as shown in the figure. 

 The blade must not bind and the pencils must swing on its edge with the 

 least possible friction. The two pencils are finnly rubber-banded together 

 so that the two notches form an opening nearly square between the pen- 

 cils. Near each end of the long pencil and on its notched side make a 

 shallow hole (c) by boring into the wood with a hard pencil having a 

 smooth, slightly blunt point. In order that the ' balance may operate 

 properly the apex of the notch in the short pencil — that is, the point 

 which rests on the knife-edge — must be exactly midway between the holes 

 in the ends of the long pencil. Slide the short pencil along the other till 

 it is in proper position, then with the point of the knife-blade cut a 

 mark (d) common to both pencils on the line where they touch. The rub- 

 ber bands should prevent the pencils from slipping when in use, but the 

 mark will show if they do slip. Two similar trays (e) are hung from the 

 ends of a long pencil. They consist of circular pieces of stiffish card- 

 board about 2 inches in diameter, suspended by means of wires curved 

 in fishhook form, the points of the hooks resting within the holes (c) 

 previously made in the pencil ends. The points of the hooks (f) are 

 bluntly and smoothly pointed, so as not to bind in the holes. Beneath the 

 trays the wires (g) are bent to hold the trays in level position, and are 

 held to the tray by pieces of gummed paper (h). ' The illustration shows 

 the trays as flat pieces of cardboard. It is better to cut the trays from 

 the edge to the center, then lap the two cut edges and glue them fast, 

 thus making a shallow dish. The wire (g) beneath the tray is then pref- 

 erably bent in circular form. Balancing the tray hook on the finger 

 shows the proper bending of the wire where it pierces the cardboard (i) to 

 make the tray hang level. A triangular piece of thin board (j), as a 

 cigar-box cover, serves to hold the knife blade in position. A block (k) 

 holds the knife handle. The knife is set high enough to permit the trays 

 to hang about one-half inch above the surface on which the balance rests. 

 For the purpose of showing slight movements of the balance in exact 

 weighing, a darning needle (1) is set in the top of the short pencil di- 

 rectly over the knife-edge and at right angles to the pencil. A pin (m) 

 is placed in the board directly over the point where the knife point 

 pierces it, and just above the end of the needle. When the device is 



