THe INFLUENCE OF Low TEMPERATURE ON Sort Bacteria 1059 
When the exposure to liquid air was continued for several hours there was 
a decrease in the number of bacteria. 
The effect of freezing seemed to be less harmful on the bacteria in 
the soil than on those in the soil dilution in the water blanks. When the 
freezing was continued for 12 hours there was a marked decrease in number 
of bacteria. It would seem that the more concentrated soil solution acted 
as a protective agency, and when the solution was weakened the effect of 
low temperatures was more marked. 
IN SANDY SOILS 
_ The soil used by Harder in his work was a rich sandy loam, and as his 
results were so marked it was thought advisable to compare a sandy loam 
soil with the Dunkirk clay soil. The results obtained when a light sandy 
soil was used are shown in table 5: 
TABLE 5. Errect or Time, TEMPERATURE, AND RATE oF THAW ON 
BactTEeRIA Count IN SANDY SOIL 
Bacteria 
Sample Treatment per gram of 
. dry soil 
1S oe ae ee Normal soil, water blank at 24° ©... 2.09.2. 05..45.. 6,400 ,000 
Die cece Nee Frozen in liquid air 5 minutes, thawed at 1°C..... 4,800,000 
Ceca ae lasienstiie Frozen in liquid air 5 minutes, thawed at 10° C..... 5,400,000 
ADAP ae Serene ck « Frozen in liquid air 5 minutes, thawed at 24° C..... 6, 800 ,000 
Siu) ol degen ts ne Frozen in liquid air 5 minutes, thawed at 30° C..... 5,600,000 
GREE enya ak) Frozen in liquid air 5 minutes, thawed at 38° C..... 4,800 ,000 
Too pe cea O aes Frozen in liquid air 1 minute, thawed at 24° C...... 5,400 ,000 
Ss id o& We ein eee Frozen in ice and salt 1 minute, thawed at 24° C.... 7,200,000 
OR eas erent iets c)iss Frozen in ice and salt 2 hours, thawed at 24° C.....} 14,000,000 
1D) ce a ot Se ee Frozen in liquid air 2 hours, thawed at 24° C.......} 11,600,000 
There was the same increase in the bacteria count due to the rate of 
thaw as noted in the earlier work, and a drop in the bacteria count when 
the temperature of the water blanks was raised to 30° C. and above. 
When the soil was frozen in ice and salt for one minute, there was an 
increase of nearly one million bacteria per gram of soil over the count for 
the normal soil. When the soil was frozen for two hours in ice and salt, 
the count increased to 14,000,000, showing an increase of 120 per cent over 
the count for the normal soil. When the soil was frozen in liquid air 
for two hours there was also a marked increase. It is evident that this 
