ELEVENTH ANNUAL YEAR BOOK— PART XI 



723 



of impurities. ]n other words, 90 per cent or (90 pounds of each 100 

 pounds I of the original seed is pure seed. In using a balance so sensi- 

 tive as the one described, a single BB shot is too heavy for use as the 

 lightest weight. We need a weight to be balanced by only a few clover 

 seeds at most. Very small shot is troublesome to handle and count, so 

 we use the larger BB shots, flattening the whole ones to prevent them 

 from rolling and cutting some into halves, quarters, eighths and six- 

 teenths. By careful selection, according to weight, a fairly uniform 

 series of whole and fracional shots can be provided. Now, the weight of 

 one-sixteenth shot is 1 per cent of the weight of 6V± shots, because 

 6% equals 100 divided by 16. So if we test a sample of seed balancing 

 6 a /4 shots any impurity balancing the 1-16 shot weight represents 1 per 

 cent of the sample tested. If the sample is twice as heavy, balancing 

 12' -j shots, the 1-16 shot weight represents one-half of 1 per cent, of the 

 whole. 



It is evident, therefore, that the means described enables one to deter- 

 mine the quantity of pure seed or of impurities in a sample to within 

 1 per cent, or even one-half of 1 per cent of the true quantity. This is 

 sufficiently close for the practical seed testing under discussion. 



The Forceps — A pair of forceps is very useful in picking up the small 

 weights used with the balance, also individual seeds. Suitable forceps 

 may be made of two thin pieces of hickory wood separated by a piece 

 of wood to which one end of each piece is fastened. The free ends are 

 flattened and pointed. A piece of spring wire bent in U shape and having 

 flattened and pointed ends serves very well as forceps. 



The Magnifiers — After the seed to be tested has been properly weighed 



it is to be separated into pure seed 

 and foreign seed or other impuri- 

 ties. This requires a magnifier. 

 Very coarse seed — such as that of 

 wheat, oats, flax, etc. — can usually 

 be examined by the aid of an ordin- 

 ary reading glass, which is to be 

 found in many homes or can be 

 bought at a cost of $1 to $2. Clover 

 seed, alfalfa seed, and the grass 

 seeds require a magnifier of higher 

 power. A very satisfactory magni- 

 fier of this kind is the tripod mag- 

 nifier. With it one can distinguish 

 all the kinds of crop seeds and prac- 

 tically all the different kinds of 

 adulterants and weed seeds. This magnifier is sold by opticians, station- 

 ers, and druggists generally throughout the country at price ranging from 

 50 to 75 cents. 



The Paper Tray — Seed is examined best over white paper, and in order 

 to prevent the loss of seed from a weighed sample a paper tray is useful. 



Fig. 14. — Magnifying glass. 



