48 SCIENCE 
the same for any series lying in the same spec- 
tral range, it will have no bearing on the con- 
troversy regarding the universal constancy of 
the Rydberg constant. For series extending far 
into the ultra-violet, this change of value may 
have some effect. 
On Bohr’s theory of the hydrogen atom, JV, 
is a known function of the charge and mass of 
the electron, and of Planck’s constant h. It is 
therefore important, on theoretical grounds, to 
know its value as accurately as possible. The 
author therefore wishes to emphasize that 
Curtis’s own determination of the hydrogen 
lines, when handled correctly, leads to a value 
of this constant of 109,678.705, while the best 
previous determinations, when converted to 
the I.A. system, yield an almost identical 
value. It is hoped that future investigators 
will use 109,678.705 rather than Curtis’s pub- 
lished value of 109,679.22. 
Raymonp T. Birce 
SYRACUSE UNIVERSITY, 
MOISTURE RATIO 
Mucu confusion has existed for years in 
interpreting the results obtained by various 
investigators on the determination of moisture 
in soils, rocks, ete. Noyes? has lately en- 
deavored to bring about a more uniform 
method of reporting the moisture content of 
soils. 
According to Bulletin No. 107, Bureau of 
Chemistry ‘Official Methods of Analysis,” 
compiled by the association of Official Agri- 
cultural Chemists, the results of soil analysis 
are calculated as per cent. of the soil dried to 
constant weight in the water oven. It is 
rather unfortunate that the official method of 
reporting results has not been uniformly fol- - 
lowed. 
One of the phrases suggested by Noyes, 
“Ratio of water to 100 parts of dry soil,” 
suggested to me the term moisture ratio. 
Such a term as “moisture ratio” on account 
of its brevity can be considered an advantage 
when preparing tables, charts, ete.; and if in- 
terpreted as defined below will not cause such 
1‘‘Reporting Moisture Results,’? H. A. Noyes, 
Science, N §., Vol. XLVI, No. 1212, p. 293. 
[N. 8S. Vou. XLVIII. No. 1228 
confusion as the terms which have been used 
in the past. 
The “moisture ratio” would mean the 
grams of water to 100 parts of the soil dried 
to constant weight at a temperature of 100- 
110°C. The terms “ oven dry” or “ absolutely 
dry” are being interpreted by some as mean- 
ing the drying of samples to 100° C., while 
others dry at higher temperatures and use the 
same terms. 
The temperature at which samples are dried 
is seldom given in papers and as it is possible 
to control most drying ovens within a range 
of 10° C., the temperature of drying soil 
samples when using the term “moisture 
ratio” would be from 100-110° C. 
I have lately made some tests on various 
electric drying ovens and found a wide range 
of temperature in some while others showed 
very little range on various shelves in the 
oven. The temperatures found on the various 
shelves in three of those tested are given in the 
table following: 
TEMPERATURE RANGE IN VARIOUS ELECTRIC OVENS 
Middle Shelf 
Oven Number Top Shelf Bottom Shelf 
1 96° C. ZOOS 147°C. 
2 94 99, 105 
3 100 96 98 
Oven No. 1 has the heating unit near the 
bottom of the oven and by tests made when 
empty as well as when full to capacity with 
soil samples showed a range in temperature 
of 51° C. 
Oven No. 2 is similar to No. 1 except that 
an extra heavy piece of asbestos was placed 
above the heating unit leaving an air space of 
about 4 inch. Tests were made as with No. 1 
and showed that the wide range of 51° C. was 
reduced to 11° C. 
Oven No. 3 is a different make of oven, 
operating on a different principle from No. 1 
or No. 2, but also had the heating unit near 
the bottom of the oven. From a large number 
of tests made under different tonditions this 
oven never showed a range greater than 5° C. 
and most of the time it was only 1 or 2 de- 
grees. 
