2 BULLETIN 1130, U. S. DEPARTMENT OF AGRICULTURE. 
plate until the preparation is properly cleared. The clearing is com- 
plete when the preparation becomes transparent. Then transfer the 
slide to the stage of the microscope and allow it to remain until no 
movement is evident in the mount when viewed under the micro- 
scope. Count the hairs and hair fragments. The magnification 
giving approximately 180 diameters here employed was obtained by 
the use of compensating ocular 12 x and 16-millimeter apochromatic 
objective. If apochromatic objectives are not available, an achro- 
matic objective with an ordinary eyepiece giving the same magnifica- 
tion is satisfactory 
COUNTING THE HAIRS. 
The counting of a slide consists in the methodical enumeration of 
all the hairs and hair fragments in the mount (Fig. 1). By means 
b-^ 
w' 
/ 
Fig. 1.— Wheat hairs (X180). 
of the mechanical stage on the microscope, no difficulty is encoun- 
tered in thoroughly and accurately covering the entire mount. Each 
hah and hair fragment is given a value of 1, the final number being 
taken as the value for the flour in question. 
SOURCES OF VARIATION IN METHOD. 
Department Bulletin 839 contains a full discussion of tests con- 
ducted to determine the sources of variation in such a method. It 
is evident that the variation in the counts made by two analysts is 
greater in the case of bran particles than in the case of hairs. 
EXAMINATION OF MILL STOCKS. 
Modern milling processes consist essentially in releasing the floury 
endosperm from the wheat grain, purifying it of bran substance, and 
eventually reducing it to what is known as flour. Any manipula- 
