--------------+-----------------------+------------------------- Circumference.| Wire Ropes |Round-link Crane-chain, | Hawser-laid. | Length of Link not | |Exceeding Five Diameters | | of the Iron. +-------+-------+-------+--------+-------+-------- | Iron. | Steel.| | | | | Safe | Safe |Weight |Diameter| Safe |Weight |Working|Working| per | of Iron|Working| per |Strain.|Strain.|Fathom.|of Link.|Strain.|Fathom. --------------+-------+-------+-------+--------+-------+--------- Inches. | Cwts. | Cwts. | Lbs. | Inches.| Cwts. | Lbs. ¾ | -- | -- | -- | 3/16| 8 | 2.1 1 | 10 | -- | 0.94| ¼ | 15 | 4.88 1¼ | 13½ | -- | 1.5 | 5/16| 22 | 7.26 1½ | 21½ | 62½ | 2.5 | ⅜ | 32 | 10.57 2 | 40 | 112 | 3.5 | 7/16| 45 | 13.0 2¼ | 50 | -- | 4.5 | ½ | 65 | 16.0 2½ | 60 | 195 | 5.75| 9/16| 75 | 21.0 2¾ | 77 | -- | 6.5 | ⅝ | 92 | 25.0 3 | 92 | 245 | 7.5 | 11/16| 112 | 29.0 3¼ | 109 | -- | 8.5 | ¾ | 135 | 36.0 3½ | 125 | 275 | 10.75| 13/16| 157 | 43.0 4 | 157½ | 450 | 13.25| ⅞ | 182 | 46.5 4½ | 210 | 545 | 17.75| 15/16| 210 | 58.0 5 | 248 | 669 | 21.5 | 1 | 240 | 63.5 --------------+-------+-------+-------+--------+-------+--------- BLOCKS, TACKLE, ETC. =Blocks= are of two kinds, _made_ and _mortised_. A made block consists of four parts: _shell_, _sheave_, _strap_, and _bush_. A mortised block is made of a single block of wood, mortised out to receive a sheave. Blocks are single, double, or treble, according to the number of sheaves. A =Tackle= is a purchase formed by reeving a rope through two or more blocks for the purpose of hoisting. A =Whip= is a purchase made by a rope rove through one single block. A =Gun-tackle Purchase= is a rope rove through two single blocks, and made fast to the strap of the upper block. The parts of all tackles between the fasts and sheave are called the _standing parts_. The parts between the sheaves are the _running parts_, and the part which is taken hold of in hoisting is called the _fall_. A =Whip upon Whip= is where the block of one whip is made fast to the fall of another. A =Luff-tackle Purchase= is a single and a double block, the end of the rope being fast to the upper part of the single block, and the fall coming from the double block. A luff-tackle upon the fall of another luff-tackle is called luff upon luff.