=Splices.= As the upper and lower chords have to be made in several lengths, securely fastened to each other, and, in order to weaken the built beam as little as possible, it is necessary to adopt some form of splicing whereby the greatest amount of tensional strength may be retained in the chord with the least amount of cutting, and yet have a secure joint.  Such a splice is shown in Pl.  II, Fig. 4, and below is a table from Vose’s Hand-book, giving reliable dimensions.

Span.  A C B B C D
Feet.  Feet.  Inches.  Feet.
50 1.00 1-1/2 1.50
100 1.25 2 2.00
150 1.75 2-1/2 2.25
200 2.00 3 2.75

This manner of splicing requires the back of the splice block to be let into the chord stick, against which it lies, about 3/4 of an inch.  To show how the various Engineers differ, as to their estimates of the sizes of the several parts of bridges, I subjoin two Tables—­one by Prof.  G.L.  Vose, a well known Engineer, and one by Jno.  C. Trautwine, an Engineer of note also—­and I would premise that a bridge built according to either would be amply strong.

TABLE FOR DIMENSIONING A HOWE TRUSS BRIDGE.  G.L.  VOSE.

End    Centre           Centre
Span.  Rise.  Panel.   Chords.     Braces.  Braces.  End Rods.  Rods.
50    10     7    2—­8 x 10   7 x  7   5 x 5  1—­1-1/8  2—­1
75    12     9    2—­8 x 10   8 x  8   5 x 5  2—­1-1/2  2—­1
100    15    11    2—­8 x 10   8 x  9   6 x 6  2—­1-3/4  2—­1
150    20    13    4—­8 x 12  10 x 10   6 x 7    3—­2    3—­1
200    25    15    4—­8 x 16  12 x 12   7 x 7    5—­2    5—­1

TABLE FOR DIMENSIONING A HOWE TRUSS BRIDGE.  JNO.  C. TRAUTWINE, C.E.

|    |    |An Upper | A Lower |  An End |A Centre|        |   End     |  Centre
Clear|    | No.| Chord.  |  Chord. |  Brace. |  Brace.|Counter.|   Rod.    |   Rod. 
Span |Rise| of |---------|---------|---------|--------|-----

---|-----------|-----------
in  | in |Pan-| No|     | No|     | No.|    | No|    | No|    | No.|      | No.|
feet.|feet|els.|Pcs|Size.|Pcs|Size.|Pcs.|Size|Pcs|Size|Pcs|S

ize|Rods|Size. |Rods|Size.
-----|----|----|---|-----|---|-----|----|----|---|----|---|-

---|----|------|----|-----
25 |  6 |  8 | 3 | 4x5 | 3 | 4x10|  2 |4x6 | 2 |5x5 | 1 |4x5 |  2 |1-5/16|  2 |  7/8
50 |  9 |  9 | 3 | 6x7 | 3 | 6x10|  2 |6x7 | 2 |5x6 | 1 |5x6 |  2 |1-5/8 |  2 |1-1/16
75 | 12 | 10 | 3 | 6x9 | 3 | 6x11|  2 |6x8 | 2 |6x6 | 1 |6x6 |  2 |1-7/8 |  2 |1-3/16
100 | 15 | 11 | 3 | 6x10| 3 | 6x12|  2 |8x9 | 2 |6x8 | 1 |6x8 |  2 |2-3/16|  2 |1-5/16
125 | 18 | 12 | 4 | 6x10| 4 | 6x13|  2 |8x10| 2 |6x9 | 1 |6x9 |  2 |2-5/8 |  2 |1-3/8
150 | 21 | 13 | 4 | 8x10| 4 | 8x14|  3 |9x10| 3 |6x9 | 2 |6x9 |  3 |2-3/8 |  3 |1-3/16
175 | 24 | 14 | 4 |10x12| 4 |10x15|  3 |9x11| 3 |8x8 | 2 |8x8 |  3 |2-5/8 |  3 |1-1/4
200 | 27 | 15 | 4 |12x12| 4 |12x16|  3 |9x12| 3 |8x10| 2 |8x10|  3 |2-7/8 |  3 |1-3/8