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ice during January and February.

Fogs.--Fogs are most frequent along this part of the Atlantic coast during

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the months of December, January, and February, but may be met at other times

during the year. Easterly winds bring them and westerly and northerly winds

clear them away. In the late fall dense fogs are liable to occur and may last

during forenoons for 2 or 3 days in succession. Autumnal fogs nearly always

clear up before noon.

It should be noted, however, that fogs are less preva

lent along this part of the Atlantic coast than they are farther north.

At

Wilmington, Del., there was an annual average of 373 hours and 23 minutes of

fog during the 24-year period 1922-45. At Fort Mifflin in the harbor of Phila

delphia, fog signals were operated 171 hours per year, averaged over the period

1939-46.

Precipitation. There is no rainy season.

The mean annual precipitation

at Philadelphia over a period of 75 years was 40.41 inches.

The mean annual

precipitation at Wilmington, Del., over a period of 25 years was 43.05 inches.

Temperature. At Philadelphia the mean maximum temperature over a period

of 73 years was 62.3 degrees Fahrenehit and the mean minimum temperature was

46.6 degrees. At Wilmington, Del., the mean maximum temperature averaged 63.7

degrees Fahrenheit per year and the mean minimum temperature averaged 44.45

degrees over a period of 25 years.

The following table of meteorological data for Wilmington, Del.,

which

is representative of conditions at localities below Philadelphia, was fur

nished by the Chamber of Commerce and the Street and Sewer Department, Wil

mington, Del. The table for Philadelphia, which shows the conditions gener

ally prevailing at the localities above Philadelphia, was furnished by the

Weather Bureau, Department of Commerce.

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20

1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946

63.6
65.8
61.4
64..2
60.9
62.15
62.55
63.7
64.7
64.7
64.7
63.9
62.5
62.2
66.2
63.7
64.8
64.5
60.5
65.2
63.7
64.2
64.5
63.8
64.5

45.4 53.9 42.7 44.6 42.4 44.4 44.2 44.2 44.7 46.5 45.44 45.2 43.4 43.8 44.0 44.9 44.9 44.5 42.0 44.0 44.8 42.9 43.4 43.6 44.5

54.5
53.9
52.0
54.3
52.1
53.25
53./47
53.9
54.7
55.6
55.1
54.5
52.9
53.17
53.6
54.3
54.9
54.5
51.3
54.5
54.2
53.5
53.8
53.7
54.5

31.92 42..12 51.85 36.82 44..13 45.59 48.37 44.53 28.27 40.37 48.24 50.10 44.29 51.02 44.444 44.55 45.79 38.77 43.55 31.96 48.07 36.82 42.63 55.74 36.45

95 96 95 92 102 110 111 106 88 95 103 lll 109 125 101 115 97 95 95 72 91 95 86 118 86

354 399 174 262 372 520 284 435 321 272 270 239 517 408 295 555 605

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255

30 143 229 354 795 45

556 Not available

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Daily mean maximum temperature, degrees Fahrenheit, for 73 years

39.5 40.9 48.6 60.9) 72.0 80.484.6 82.5 76.0 65.9 52.6 42.8

62.3

Daily mean minimum temperature, degrees Fahrenheit, for 73 years

25.7 26.9 33.0 43.3 53.8 62.4 67.867.1 60.0 49.7 38.8 29.8

46.6

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3.30 3.32 3.39 3.05 3.26 3.244..15 4.62 3.14 2.81 2.70 3.43 40.41

Hours of operation of fog signals at Fort Mifflin, 1939-1946

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There are no existing bridges across the Delaware River below Philadelphia.

Plans have been formulated and a permit has been issued for the construction of

a high-level fixed span bridge to cross the Delaware River between Pigeon Point

at Wilmington, Del., and Deepwater, N. J. Mantua Creek at Paulsboro, N. J.,

is

crossed by two bridges. Three bridges cross the Delaware River connecting

Philadelphia Harbor with the localities across the river and one connects the

city of Camden with Petty Island. Above Philadelphia one bridge connects the

cities of Burlington and Bristol. There is also one bridge at the terminus of

the 12-foot channel at Trenton, N. J.

The table on page 17 gives full details

concerning the location and description of the bridges across Mantua Creek and

the Delaware River.

Bridge Regulations

Regulations governing the operation of the bridges over the Delaware River

are quoted below. These regulations also pertain to the bridges over the Schuyl

kill River in Philadelphia Harbor, which are described in Port Series No. 7,

covering the Ports of Philadelphia, Pa., and Camden, Gloucester, Delair, and

Riverton, N. J.

1. Signals.--Then at any time during the day or night any vessel, tug,

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Bridges crossing Mantua Creek and the Delaware River

Channel Spans
Clear width normal to Clear height, lowest
channel

point of superstruc-
ture above

Type

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Pennsylvania Railroad Bridge, Paulsboro,

N, J.
New Jersey State Highway Bridge, Pauls-
boro, N. J.

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Pennsylvania-New Jersey Highway Toll
Bridge, Race Street, Philadelphia, to
Pearl Street, Camden.
Pennsylvania Railroad Bridge, Camden to

Petty Island.
Pennsylvania Railroad Delair Bridge
Tacony-Palmyra Highway Bridge
Burlington-Bristol Highway Bridge

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Miles
above
mouth

Name

Mantua Creek

1.444

1.68

Delaware River

100,2

103.2

104.6
107.2
117.8

133.4

Pennsylvania Railroad Bridge at Trenton

60

60

60

35.6

8.2

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When lift span is down, height at mean low water is 10 feet and at mean high water, 5 feet.
Distances on the Delaware River are referred to Delaware Capes.
Clearance given is for a channel width of 800 feet in the middle of the span.
When span is down, height at mean low water is 67.5 feet and at mean high water, 62.3 feet.

or other water craft unable to pass under the bridge approaches it with the intention of passing through the draw, the signal for the draw to be opened shall be three blasts of a whistle or horn blown on the vessel or craft.

If the draw is ready to be opened immediately when the signal is given on the vessel or craft, the signal shall be answered immediately by two blasts of a whistle or horn blown on the bridge; and if the draw is not ready to be opened immediately on the signal being given on the craft, the signal shall be answered immediately by one blast of a whistle or horn blown on the bridge.

2. Opening the draw. Upon hearing or perceiving the prescribed signal, the bridge tender shall immediately clear the draw span and open the draw to its full extent for the passage of the vessel or other craft: Provided, That the draw of a railroad bridge need not be opened when there is a train in the bridge block approaching the bridge with the intention of crossing, nor within five minutes of the known time of passage of a scheduled passenger, mail, or express train; but in no event, except in case of breakdown of the operating machinery, shall the opening of the draw be delayed more than five minutes in the case of a highway bridge, nor more than 10 minutes in the case of a railroad bridge: And provided further, That the draw need not be opened for the passage of a tug or other craft equipped with a movable stack or mast which can readily be lowered so as to permit its passage under the closed draw, unless such craft has in tow a vessel which is unable to pass under the closed draw, or by reason of stress of weather it is unsafe to lower such stack or mast.

3. Interference with operation.--Vehicles, street cars, locomotives, and trains shall not be stopped on the draw spans, nor shall locomotives or trains be stopped in the bridge blocks of railroad bridges in such manner as to delay the operation of the draw, except in case of urgent necessity; nor shall vessels be moored to the bridge fenders or so maneuvered as to unnecessarily hinder or delay the closing of the draw; but all passages over, through, or under the bridges shall be prompt, to avoid delay to either land or water traffic.

4. Hinged stacks and masts.--Each tug, towboat barge, and other small craft regularly and habitually navigating the Schuylkill River shall be subject to inspection and measurement by The District Engineer, Philadelphia District, Corps of Engineers, in charge of the district, to determine the exact height above the water surface of its pilot or deck houses, when such vessel is in its ordinary trim; end the said district engineer is hereby empowered to decide in each case, whether or not the vessel shall be equipped with hinged or removable stacks, masts, and flagpoles, which can be lowered to enable the vessels to pass under the closed draw of any or all of the bridges. If the district engineer decides that such action should be taken, he shall notify the vessel owner and the bridge owner of his decision, specifying a reasonable time for making the alterations; and after the expiration of the time specified, the drav need not be opened for the passage of such vessel unless it has in tow a vessel unable to pass under the closed draw, or by reason of stress of weather it is unsafe to lower such stack or mast.

5. Operating machinery.-All drawbridges to which these regulations apply shall be equipped with adequate quick-operating power machinery for opening and closing the draw, and this machinery shall at all times

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