6 BULLETIN 1013, IT. S. DEPARTMENT OF AGRICULTURE. 
products. The shaded portion marked " invisible loss " is the differ- 
ence in the weight of the wheat with the temper water added and the 
total weight of mill products obtained from milling. With each 
increase of relative humidity there is an appreciable decrease in the 
invisible loss occurring during milling and a proportionate increase 
in the total yield of mill products. For example, the average in- 
visible loss resulting from milling 11 samples at relative humidities 
ranging from 25 to 29 per cent, inclusive, was 5.2 per cent, while in 
milling 59 samples at relative humidities ranging from 65 to 69 per 
cent,. the average invisible loss amounted to only 3.3 per cent. This 
loss in weight is due principally to the evaporation of moisture con- 
tained in the wheat, and, except in the cases of low atmospheric 
humidity, amounted to less than the quantity of water added in tem- 
pering. In other words, the weight lost through the evaporation of 
moisture during milling was greater than the weight of the temper 
water added when the samples were milled at relative humidities 
lower than 35 to 39 per cent and less when milled at higher relative 
humidities. 
COMPARISON OF THE INFLUENCE OF RELATIVE HUMIDITY AND 
OF MOISTURE CONTENT OF WHEAT ON MILLING YIELDS. 
That both the relative humidity of the air and the moisture content 
of the untempered wheat have a considerable influence on the weight 
lost or gained during milling as compared with the weight of the 
wheat before tempering is quite evident from figure 3. In preparing 
this diagram the samples were 'grouped according to certain ranges 
in the percentages of moisture contained in the wheat samples before 
tempering, and a separate curve was made for each group. This 
scheme of diagramming makes it possible to show the relation of 
both relative humidity =jand moisture content to the total yield of 
mill products. 
The curves show that the higher yields are associated with the 
higher relative humidities and with the wheats of lower moisture 
content. Each 10 per cent increase in relative humidity above 35 
per cent shows an average increase of about one-half of 1 per cent in 
the total weight of the products obtained, and each decrease of 1 per 
cent in the moisture content of the wheat before tempering shows 
about six-tenths of 1 per cent increase in yield. Compared with the 
weight of the wheat before tempering, the samples containing from 
9 to 9.9 per cent moisture showed a net gain in weight of total mill 
products for all relative humidities given, while the samples contain- 
ing from 12 to 12.9 per cent moisture before tempering showed a net 
loss in weight of total mill products except for relative humidities 
higher than 60 to 69 per cent. The greatest average gain in weight 
