WATER-CONTENT 27 
than I per cent from the dug sample used as a check. As soon as dug, the 
core is pressed out of the geotome by the plunger directly into an air-tight 
soil can, Bottles may be used as containers, but tin cans are lighter and 
more durable. Aluminum cans have been devised for this purpose, but on 
account of the expense, ‘‘Antikamnia” cans have been used instead. These 
are tested, and those that are not water-tight are rejected, although it has 
been found that, even in these, ordinary soils do not lose an appreciable 
amount of water in twenty-four hours. The lid should be screwed on as 
quickly as possible, and, as an added precaution, the cans are kept in a close 
case until they have been weighed. The cans are numbered consecutively 
on both lid and side in such a way that the number may be read at a glance. 
The numbers are painted, as a label wears off too rapidly, and scratched 
numbers are not quickly 
discerned. 
44, Weighing, Al- 
though soil samples 
have -been kept in tight 
cans outside of cases 
for several days without 
losing a milligram of 
moisture, the safest plan 
is to make it a rule to 
weigh cans as quickly 
as possible after bring- 
ing them in from the 
field. Moreover, when 
delicate balances are 
available, it- is a good 
practice to weigh to the 
milligram. At remote 
bases, however, and Fig. 4. Field balance. 
particularly in the field, 
and on reconnaissance, where delicate, expensive instruments are out of 
place, coarser balances, which weigh accurately to one centigram, give 
satisfactory results. The study of-efficient water-content values has already 
gone far enough to indicate that differences less than 1 per cent are neg- 
ligible. Indeed, the soil variation in a single square meter is often as 
great as this. The greatest difference possible in the third place, i. e., that 
of 9 milligrams, does not produce a difference of .1 of I per cent in 
the water-content value. ‘In consequence, such strong portable balances 
as Bausch & Lomb 12308 ($2), which can be carried anywhere, give entirely 
