BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
305 
by a drop in temperature due to rain, cloudiness, or other factors. As an example, 
in July, 1916, the surface temperatures at practically all stations on the bay were 
lower than those a few meters below, a condition which was not found usually during 
continued fair weather on the cruises of the summer months. At area R the tempera- 
tures were as follows: Surface 25.2° C., 8 meters 25.6° C., 16 meters 25.3° C., 26 
meters 24.5° C., 36 meters 25.0° C., 46 meters 25.2° C. During June of the same 
year at area R a summer condition was found — for example, surface 20.3° C.,9 meters 
19.3° C., 18 meters 17.7° C., 21 meters 17.6° C., 27 meters 17.2° C., 31 meters 17.0° C., 
and 41 meters 17.2° C. The records of the United States Weather Bureau show that 
during the July cruise there were heavy rains in regions about and on Chesapeake 
Bay. It seems highly probable that they account for the low surface temperatures. 
(See Kriimmel, 1911.) An equally interesting cruise is that of August, 1920. Areas 
G, F, A, and B, near the mouth of the bay, were visited on August ,22 and showed a 
very marked thermocline — for example, at G, surface 27.0° C., 10 meters 20.2° C., 20 
meters 17.2° C., and 23.6 meters 15.5° C. Similar exceptionally high surface temper- 
atures, even for summer months, were found at areas F, A, and B. This condition 
seems to be traceable to high air temperatures in that region. (Maximum at Norfolk 
90° F. (32.2° C.) and minimum 68° F. (20.0° C.) on August 20.) Farther up the 
bay the air temperatures and the surface-water temperatures were much lower. 
(Maximum air temperature at Baltimore 70° F. (21.1° C.) and minimum 68° F. 
(20.0° C.) on August 20.) The thermocline was obliterated at practically every 
station and frequently the surface temperatures were lower than those a few meters 
below. Observations made at area U, near Baltimore, on August 26, showed, as an 
example, surface 23.5° C., 5 meters 24.4° C., 11 meters 24.2° C., at 12 noon. The 
night before these data were obtained the temperature at Baltimore had dropped to 
as low as 64° F. (17.8° C.) with a daytime maximum of 74° F. (23.3° C.), according 
to the records of the United States Weather Bureau. Several days of rainy weather 
in the region of Baltimore and Washington had preceded August 20, so it seems 
probable that the rain was also a factor in bringing about the lowered temperatures 
at the surface. 
Ice floes have an effect on the distribution of temperature in the Chesapeake 
Bay. This was evident at area U during January, 1921. Observations were made 
of temperature and salinity at 1%-hour intervals for a good part of 24 hours, but 
toward the end of that period observations were discontinued on account of the float- 
ing ice which interfered with the instruments. Before the ice disturbed the work, the 
typical distribution of winter temperature was observed hour after hour — for example, 
at 4.05 a. m., surface 2.1° C., 5 meters 2.9° C., 11.9 meters 3.5° C. When the ice 
floes appeared at 5.35 a. m., however, a mesothermous distribution occurred as follows: 
Surface 0.3° C., 5 meters 1.6° C., 11.9 meters 0.9° C. 
SEASONAL DISTRIBUTION OF WATER TEMPERATURE AND SALINITY 
TEMPERATURE OF WATER DURING WINTER AND INFLUENCE OF OCEANIC WATER 
The range of temperature values observed from the mouth of the bay toward the 
head varied with the season. A study of the winter data at the surface and at the 
20 and 30 meter depths along the deep-water channel, areas A, J, L, R, S, X, Y, and 
U, shows a decreasing range with some irregularities from the mouth toward the head, 
as shown in Tables 1 and 4. The largest irregularities in the decreasing range of the 
30-meter temperatures occur at areas J and L, which are close to the mouth of the 
