Ig11] BURNS—HURON RIVER VALLEY 10g 
ture of the air fell near the freezing point, and hence the early 
spring and late fall data were untrustworthy. In any temper- 
ature of the air ranging above 7° C., the records were found to be 
reliable. 
The temperature of the air at First Sister Lake, in the floating 
sedge zone, compared with that on high ground in Ann Arbor at 
7 A.M. is given below. 
Fic. 2.—Thermographs in the bog shrub zone at First Sister Lake; the one on 
the left is headin air, the other soil temperature; photograph by STEELE. 
TABLE I 
DIFFERENCES IN TEMPERATURE IN BOG AND UPLAND; BOTH RECORDS WERE MADE 
WITH THERMOGRAPHS 
WEEK HIGHEST LowEstT 
Bog Upland Bog Upland 
April 26- May ee be ig © 14°7C —1°C, a°4 C. 
3—May to. 0. ter: 7 10.1 4 9 
Mace 10-Msy Boe | II 18 —I fe) 
May t7-May G4 on yous 10 14.2 —2 3.6 
Table I shows that in the morning the temperature of the air 
in the bog is several degrees lower than that of the upland. The 
only exception in a much larger collection of data than published 
