From: David I. Bell (dbell@pdact.pd.necisa.oz.au)
Date: Fri Sep 25 1992 - 13:01:02 UTC

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----------------- [Continued from previous mail article] --------------------

As expected, the sparks at the back of the tagalong can be used to attach
further tagalongs. Following is a relatively small tagalong that can be
attached.

[Period 4 spaceship with a tagalong to a tagalong (speed c/4)]
..........................................O..OO.
..........OO.O............OO..............O..OOO
......OOO.O.OOO........O.OOO..............O....O
..O.O..........O...OO.O....O.........OOOOO......
OO....OO.....O...OOOO.O...OO..........O.OO......
..O.OO..O....OOO.O.....OOOO.O...O.OOOO..........
........O....O.............OOO...O..............
..O.OO..O....OOO.O.....OOOO.O...O.OOOO..........
OO....OO.....O...OOOO.O...OO..........O.OO......
..O.O..........O...OO.O....O.........OOOOO......
......OOO.O.OOO........O.OOO..............O....O
..........OO.O............OO..............O..OOO
..........................................O..OO.

Two copies of the above spaceship can be used to provide the required back
end for attaching a "MWSS" tagalong. This is shown below.

[Two period 4 spaceships connected by "MWSS" tagalong (speed c/4)]
..........................................O..OO...................
..........OO.O............OO..............O..OOO..................
......OOO.O.OOO........O.OOO..............O....O..................
..O.O..........O...OO.O....O.........OOOOO........................
OO....OO.....O...OOOO.O...OO..........O.OO........................
..O.OO..O....OOO.O.....OOOO.O...O.OOOO............................
........O....O.............OOO...O......................O.........
..O.OO..O....OOO.O.....OOOO.O...O.OOOO................O...........
OO....OO.....O...OOOO.O...OO..........O.OO...........O.....O......
..O.O..........O...OO.O....O.........OOOOO..........O.......O.....
......OOO.O.OOO........O.OOO..............O....O.O..O.OOOOO.O....O
..........OO.O............OO..............O..OOO.O.O..O....OOO.O.O
..........................................O..OO....OOO.........O.O
..................................................................
..........................................O..OO....OOO.........O.O
..........OO.O............OO..............O..OOO.O.O..O....OOO.O.O
......OOO.O.OOO........O.OOO..............O....O.O..O.OOOOO.O....O
..O.O..........O...OO.O....O.........OOOOO..........O.......O.....
OO....OO.....O...OOOO.O...OO..........O.OO...........O.....O......
..O.OO..O....OOO.O.....OOOO.O...O.OOOO................O...........
........O....O.............OOO...O......................O.........
..O.OO..O....OOO.O.....OOOO.O...O.OOOO............................
OO....OO.....O...OOOO.O...OO..........O.OO........................
..O.O..........O...OO.O....O.........OOOOO........................
......OOO.O.OOO........O.OOO..............O....O..................
..........OO.O............OO..............O..OOO..................
..........................................O..OO...................

Another small tagalong can be attached to the sparky tagalong. This
tagalong only requires a loose connection to the base ship, and so it can
also be attached to many other spaceships. The following shows two copies
of it attached to the sparky tagalong using two different sparks.

[Period 4 spaceship with small tagalongs (speed c/4)]
 ......................................O.O....
 ..........OO.O............OO......OOOOOOO..OO
 ......OOO.O.OOO........O.OOO.....OOOO.....O..
 ..O.O..........O...OO.O....O....OO.OO.O......
 OO....OO.....O...OOOO.O...OO......O..........
 ..O.OO..O....OOO.O.....OOOO.O................
 ........O....O.............OOO...............
 ..O.OO..O....OOO.O.....OOOO.O................
 OO....OO.....O...OOOO.O...OO.................
 ..O.O..........O...OO.O....O.................
 ......OOO.O.OOO........O.OOO.....O...........
 ..........OO.O............OO...OO.OO.O.......
 ................................OOOO.....O...
 .................................OOOOOOO..OO.
 .....................................O.O.....

Unfortunately this tagalong cannot be attached to itself. However, since
it has a back end which is common to many slow period 4 spaceships, many
tagalongs can be attached to two copies of it. An example of this is
shown below, where the previously described "LWSS" tagalong is pulled.

[Two period 4 spaceships pulling "LWSS" tagalong (speed c/4)]
 ..........OO.O............OO.................................
 ......OOO.O.OOO........O.OOO.................................
 ..O.O..........O...OO.O....O.................................
 OO....OO.....O...OOOO.O...OO.................................
 ..O.OO..O....OOO.O.....OOOO.O................................
 ........O....O.............OOO...............................
 ..O.OO..O....OOO.O.....OOOO.O................................
 OO....OO.....O...OOOO.O...OO......O..............OOOO........
 ..O.O..........O...OO.O....O....OO.OO.O.........O....OO......
 ......OOO.O.OOO........O.OOO.....OOOO.....O...O.O...........O
 ..........OO.O............OO......OOOOOOO..OO.....O....O.OO.O
 ......................................O.O.....OOOO...O.O.O...
 .............................................................
 ......................................O.O.....OOOO...O.O.O...
 ..........OO.O............OO......OOOOOOO..OO.....O....O.OO.O
 ......OOO.O.OOO........O.OOO.....OOOO.....O...O.O...........O
 ..O.O..........O...OO.O....O....OO.OO.O.........O....OO......
 OO....OO.....O...OOOO.O...OO......O..............OOOO........
 ..O.OO..O....OOO.O.....OOOO.O................................
 ........O....O.............OOO...............................
 ..O.OO..O....OOO.O.....OOOO.O................................
 OO....OO.....O...OOOO.O...OO.................................
 ..O.O..........O...OO.O....O.................................
 ......OOO.O.OOO........O.OOO.................................
 ..........OO.O............OO.................................

The advantage of this method of connecting spaceships is that the spacing
between the pairs of base spaceships can be varied to suit the tagalong
which is being pulled. Another example of this is shown later.

Following are several larger tagalongs to the sparky tagalong. Most of
these react substantially with the sparks and therefore cannot be moved
to another base spaceship.

[Several period 4 "sparky" spaceships with large tagalongs (speed c/4)]
 ...........................................O..OO.
 ..........OO.O............OO.....OO........O..OOO
 ......OOO.O.OOO........O.OOO...OO..........O....O
 ..O.O..........O...OO.O....O.....OO...OOOOO......
 OO....OO.....O...OOOO.O...OO.....O.O...O.OO......
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOOO..........
 ........O....O.............OOO...................
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOOO..........
 OO....OO.....O...OOOO.O...OO.....O.O...O.OO......
 ..O.O..........O...OO.O....O.....OO...OOOOO......
 ......OOO.O.OOO........O.OOO...OO..........O....O
 ..........OO.O............OO.....OO........O..OOO
 ...........................................O..OO.

 ...........................................O.O....
 ..........OO.O............OO.....OO.....OOOOOO..OO
 ......OOO.O.OOO........O.OOO...OO.....OOOO.....O..
 ..O.O..........O...OO.O....O.....OO...OO.O.O......
 OO....OO.....O...OOOO.O...OO.....O..O..O..........
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOO............
 ........O....O.............OOO....................
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOO............
 OO....OO.....O...OOOO.O...OO.....O..O..O..........
 ..O.O..........O...OO.O....O.....OO...OO.O.O......
 ......OOO.O.OOO........O.OOO...OO.....OOOO.....O..
 ..........OO.O............OO.....OO.....OOOOOO..OO
 ...........................................O.O....

 .........................................O.O.O...
 ..........OO.O............OO.....OO........O.OO.O
 ......OOO.O.OOO........O.OOO...OO.....O.........O
 ..O.O..........O...OO.O....O.....OO..O...OO......
 OO....OO.....O...OOOO.O...OO.....O..O..OO........
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOO...........
 ........O....O.............OOO...................
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOO...........
 OO....OO.....O...OOOO.O...OO.....O..O..OO........
 ..O.O..........O...OO.O....O.....OO..O...OO......
 ......OOO.O.OOO........O.OOO...OO.....O.........O
 ..........OO.O............OO.....OO........O.OO.O
 .........................................O.O.O...

 ..........OO.O............OO.....OO.............
 ......OOO.O.OOO........O.OOO...OO......O...OO...
 ..O.O..........O...OO.O....O.....OO...OOO.OOO...
 OO....OO.....O...OOOO.O...OO.....O.O.....O...OOO
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOOOOOOOOOO.O
 ........O....O.............OOO..................
 ..O.OO..O....OOO.O.....OOOO.O...O.OOOOOOOOOOOO.O
 OO....OO.....O...OOOO.O...OO.....O.O.....O...OOO
 ..O.O..........O...OO.O....O.....OO...OOO.OOO...
 ......OOO.O.OOO........O.OOO...OO......O...OO...
 ..........OO.O............OO.....OO.............

 ..........OO.O............OO......OOO.O...OO...O..
 ......OOO.O.OOO........O.OOO......OO.....OOOO.OO..
 ..O.O..........O...OO.O....O...OO.O...O..O.O......
 OO....OO.....O...OOOO.O...OO...OO.....O....OO...OO
 ..O.OO..O....OOO.O.....OOOO.O...O.OO...OOO.OOOOOOO
 ........O....O.............OOO....................
 ..O.OO..O....OOO.O.....OOOO.O...O.OO...OOO.OOOOOOO
 OO....OO.....O...OOOO.O...OO...OO.....O....OO...OO
 ..O.O..........O...OO.O....O...OO.O...O..O.O......
 ......OOO.O.OOO........O.OOO......OO.....OOOO.OO..
 ..........OO.O............OO......OOO.O...OO...O..

 ......................................O........OO.......
 ..........OO.O............OO..........O...O...O.O.......
 ......OOO.O.OOO........O.OOO......OO..O.......O.OO......
 ..O.O..........O...OO.O....O...O.OOO...O.OO..O..OO......
 OO....OO.....O...OOOO.O...OO...OO...O...O...O.O..OO.O...
 ..O.OO..O....OOO.O.....OOOO.O...OOOO..............O.O...
 ........O....O.............OOO.............OOO........OO
 ..O.OO..O....OOO.O.....OOOO.O...OOOO..............O.O...
 OO....OO.....O...OOOO.O...OO...OO...O...O...O.O..OO.O...
 ..O.O..........O...OO.O....O...O.OOO...O.OO..O..OO......
 ......OOO.O.OOO........O.OOO......OO..O.......O.OO......
 ..........OO.O............OO..........O...O...O.O.......
 ......................................O........OO.......

The tagalong for the last spaceship shown above can also be used to connect
two parallel spaceships using the small extension tagalong. For this to
occur, a small modification of the small extension tagalong is required.
This is shown below.

[Two period 4 spaceships pulling a tagalong (speed c/4)]
 ..........OO.O............OO.........................................
 ......OOO.O.OOO........O.OOO.........................................
 ..O.O..........O...OO.O....O.........................................
 OO....OO.....O...OOOO.O...OO.........................................
 ..O.OO..O....OOO.O.....OOOO.O........................................
 ........O....O.............OOO.......................................
 ..O.OO..O....OOO.O.....OOOO.O........................................
 OO....OO.....O...OOOO.O...OO......O..................................
 ..O.O..........O...OO.O....O....OO.OO.O..............................
 ......OOO.O.OOO........O.OOO.....OOOO.....O.O.......O........O.......
 ..........OO.O............OO......OOOOOOO..O..O....O.OO....OO........
 ......................................O.O.....O...O....OO....O.......
 ...............................................OOOOOO.....O..O.......
 ...............................................O..O..O.OO.OOO...O....
 ...............................................OOO........O....OO....
 .........................................................OO.......OOO
 ...............................................OOO........O....OO....
 ...............................................O..O..O.OO.OOO...O....
 ...............................................OOOOOO.....O..O.......
 ......................................O.O.....O...O....OO....O.......
 ..........OO.O............OO......OOOOOOO..O..O....O.OO....OO........
 ......OOO.O.OOO........O.OOO.....OOOO.....O.O.......O........O.......
 ..O.O..........O...OO.O....O....OO.OO.O..............................
 OO....OO.....O...OOOO.O...OO......O..................................
 ..O.OO..O....OOO.O.....OOOO.O........................................
 ........O....O.............OOO.......................................
 ..O.OO..O....OOO.O.....OOOO.O........................................
 OO....OO.....O...OOOO.O...OO.........................................
 ..O.O..........O...OO.O....O.........................................
 ......OOO.O.OOO........O.OOO.........................................
 ..........OO.O............OO.........................................

Going back to the small period 4 ship without the sparky tagalong, Hartmut
found some other tagalongs as shown below.

[More tagalongs for smallest slow period 4 spaceship (speed c/4)]
 ..........................OO.O.O...
 ..........OO.O..........O....O.OO.O
 ......OOO.O.OOO........O..........O
 ..O.O..........O...OO.O....OO......
 OO....OO.....O...OOOO.O.OOO........
 ..O.OO..O....OOO.O.....O...........
 ........O....O.....................
 ..O.OO..O....OOO.O.....O...........
 OO....OO.....O...OOOO.O.OOO........
 ..O.O..........O...OO.O....OO......
 ......OOO.O.OOO........O..........O
 ..........OO.O..........O....O.OO.O
 ..........................OO.O.O...

 .........................O........OO.......
 ..........OO.O...........O...O...O.O.......
 ......OOO.O.OOO..........O.......O.OO......
 ..O.O..........O...OO.O...O.OO..O..OO......
 OO....OO.....O...OOOO.OO...O...O.O..OO.O...
 ..O.OO..O....OOO.O...................O.O...
 ........O....O................OOO........OO
 ..O.OO..O....OOO.O...................O.O...
 OO....OO.....O...OOOO.OO...O...O.O..OO.O...
 ..O.O..........O...OO.O...O.OO..O..OO......
 ......OOO.O.OOO..........O.......O.OO......
 ..........OO.O...........O...O...O.O.......
 .........................O........OO.......

 ..................................OO..........O..OO.
 ..........OO.O.................O.O..O.........O..OOO
 ......OOO.O.OOO........O...OOOOO.OOOO.........O....O
 ..O.O..........O...OO.O.O....OOO....OO...OOOOO......
 OO....OO.....O...OOOO.O...O......OO..OO...O.OO......
 ..O.OO..O....OOO.O.....OOOOOOOOOO...OO.OOO..........
 ........O....O......................................
 ..O.OO..O....OOO.O.....OOOOOOOOOO...OO.OOO..........
 OO....OO.....O...OOOO.O...O......OO..OO...O.OO......
 ..O.O..........O...OO.O.O....OOO....OO...OOOOO......
 ......OOO.O.OOO........O...OOOOO.OOOO.........O....O
 ..........OO.O.................O.O..O.........O..OOO
 ..................................OO..........O..OO.

The following two tagalongs are almost identical to two of the tagalongs
for the sparky tagalong already given. A small modification of their front
ends allows them to be connected directly to the small period 4 spaceship,
thus avoiding the use of the sparky tagalong.

[Small period 4 spaceships with tagalongs (speed c/4)]
 .................................O.O....
 ..........OO.O................OOOOOO..OO
 ......OOO.O.OOO........O....OOOO.....O..
 ..O.O..........O...OO.O.O...OO.O.O......
 OO....OO.....O...OOOO.O...O..O..........
 ..O.OO..O....OOO.O.....OOOOO............
 ........O....O..........................
 ..O.OO..O....OOO.O.....OOOOO............
 OO....OO.....O...OOOO.O...O..O..........
 ..O.O..........O...OO.O.O...OO.O.O......
 ......OOO.O.OOO........O....OOOO.....O..
 ..........OO.O................OOOOOO..OO
 .................................O.O....

 ..........OO.O...............O..............
 ......OOO.O.OOO........O....O...OO..........
 ..O.O..........O...OO.O.O...O...OO..........
 OO....OO.....O...OOOO.O...O.......OO.O.OO...
 ..O.OO..O....OOO.O.....OOOOOOOOOOOO.O..OOO.O
 ........O....O...........................O.O
 ..O.OO..O....OOO.O.....OOOOOOOOOOOO.O..OOO.O
 OO....OO.....O...OOOO.O...O.......OO.O.OO...
 ..O.O..........O...OO.O.O...O...OO..........
 ......OOO.O.OOO........O....O...OO..........
 ..........OO.O...............O..............

Here are several other large spaceships which begin the same as the small
slow period 4 "traffic-lights" spaceship, but then quickly diverge. They
have the usual back ends and therefore can attach to many tagalongs.

[Some large period 4 spaceships (speed c/4)]
 .......O.........................O..........
 .....OO............O...........OO......O....
 .......O...OO.....O.O....OOO.OOO...O...O....
 .....OOO...OOO....OO.....OO.OOO.....O.O.OO..
 ....OO........OOOO...OO...O.O.OOOOO.OO.O.O..
 ..O....O...O..O.OO...OOO.O.O........OOO...OO
 OO....O..O.O..OOO.............OOOOO....OO.OO
 ..O..OOO.............OOOOOOOOOO..O.O..O...O.
 ....................O..........O......O.....
 ..O..OOO.............OOOOOOOOOO..O.O..O...O.
 OO....O..O.O..OOO.............OOOOO....OO.OO
 ..O....O...O..O.OO...OOO.O.O........OOO...OO
 ....OO........OOOO...OO...O.O.OOOOO.OO.O.O..
 .....OOO...OOO....OO.....OO.OOO.....O.O.OO..
 .......O...OO.....O.O....OOO.OOO...O...O....
 .....OO............O...........OO......O....
 .......O.........................O..........

 .......O...................................OO............
 .....OO............O.........OO.............O............
 .......O...OO.....O.O.......O..O..OO.....OO.OOOOO........
 .....OOO...OOO....OO.......O......OO.....OOO.OOOOOO......
 ....OO........OOOO...OO........OO...OO...O..O.OOOOO......
 ..O....O...O..O.OO...OOO...O.OOOOO....O.O.O..O.....O....O
 OO....O..O.O..OOO.......O.O.OO..O....O....O........O..OOO
 ..O..OOO.............OOOOO....OOOO....O...OOOO.....O..OO.
 ....................O....................................
 ..O..OOO.............OOOOO....OOOO....O...OOOO.....O..OO.
 OO....O..O.O..OOO.......O.O.OO..O....O....O........O..OOO
 ..O....O...O..O.OO...OOO...O.OOOOO....O.O.O..O.....O....O
 ....OO........OOOO...OO........OO...OO...O..O.OOOOO......
 .....OOO...OOO....OO.......O......OO.....OOO.OOOOOO......
 .......O...OO.....O.O.......O..O..OO.....OO.OOOOO........
 .....OO............O.........OO.............O............
 .......O...................................OO............

 .......O...................................OO...........
 .....OO............O.........OO.............O...........
 .......O...OO.....O.O.......O..O..OO.....OO.OOOO........
 .....OOO...OOO....OO.......O......OO.....OOO.OOOOO......
 ....OO........OOOO...OO........OO...OO...O..O.OOOO......
 ..O....O...O..O.OO...OOO...O.OOOOO....O.O.O..O....O....O
 OO....O..O.O..OOO.......O.O.OO..O....O....O.......O..OOO
 ..O..OOO.............OOOOO....OOOO....O...OOOO....O..OO.
 ....................O...................................
 ..O..OOO.............OOOOO....OOOO....O...OOOO....O..OO.
 OO....O..O.O..OOO.......O.O.OO..O....O....O.......O..OOO
 ..O....O...O..O.OO...OOO...O.OOOOO....O.O.O..O....O....O
 ....OO........OOOO...OO........OO...OO...O..O.OOOO......
 .....OOO...OOO....OO.......O......OO.....OOO.OOOOO......
 .......O...OO.....O.O.......O..O..OO.....OO.OOOO........
 .....OO............O.........OO.............O...........
 .......O...................................OO...........

The last two spaceships shown above are related and are reminiscent of the
"MWSS" and "LWSS" tagalongs shown before. But the MWSS-like spark is hidden
just behind an edge, and so is not of much use.

The following spaceship is one of the more unusual slow period 4 spaceships
because of the fact that it is reminiscent of two of the period 3 spaceships.
The section in the last 13 columns appears at the front to be like the
"dart" period 3 spaceship. And the part just in front of that appears to
be like the back of of sequence of "turtle"-like back ends. And yet these
period 3 shapes work here in period 4.

[Large period 4 spaceship (speed c/4)]
 .......O...........................................O.O....
 .....OO............O.........OO....................O...O..
 .......O...OO.....O.O.......O..O..OO...............O..OO..
 .....OOO...OOO....OO.......O......OO.................O.O..
 ....OO........OOOO...OO........OO...OO.....OO..........O..
 ..O....O...O..O.OO...OOO...O.OOOOO....O.OOO.......O....OO.
 OO....O..O.O..OOO.......O.O.OO..O....O....O....O.OO....O.O
 ..O..OOO.............OOOOO....OOOO....O..O...OO......O.O..
 ....................O....................O...OO...OOOO..OO
 ..O..OOO.............OOOOO....OOOO....O..O...OO......O.O..
 OO....O..O.O..OOO.......O.O.OO..O....O....O....O.OO....O.O
 ..O....O...O..O.OO...OOO...O.OOOOO....O.OOO.......O....OO.
 ....OO........OOOO...OO........OO...OO.....OO..........O..
 .....OOO...OOO....OO.......O......OO.................O.O..
 .......O...OO.....O.O.......O..O..OO...............O..OO..
 .....OO............O.........OO....................O...O..
 .......O...........................................O.O....

On 8 September 1992, Hartmut Holzwart found a period 4 component which can
be repeatably placed alongside itself, and whose ends are terminated with
spaceships which have the "MWSS" spark. This was found by a special
search feature he implemented which looked for spaceships in a cylindrical
area. This is the first known component for making short and wide c/4
period 4 spaceships.

[First known component for short wide slow period 4 spaceships (speed c/4)]
 .......O..OO.................
 ......O...OO.....OOO.........
 .....OO......O.OOOOOOO.......
 .O...OO..O..OOO..OOOOO.......
 .O.......O......O.....O....O.
 OO..O....O..O.OO......O..OOO.
 .O.OO......O....O.....O..OO..
 .O.OO........................
 .O.OO......O....O.....O..OO..
 OO..O....O..O.OO......O..OOO.
 .O.......O......O.....O....O.
 .O...OO..O..OOO..OOOOO.......
 .....OO......O.OOOOOOO.......
 ......O...OO.....OOO.........
 .......O..OO.................
 .................OOO..O......
 ................OOOO..O......
 ................O.....O.OO...
 ................O.OOO...OOO.O
 .................O.O......O.O
 ................O.OOO...OOO.O
 ................O.....O.OO...
 ................OOOO..O......
 .................OOO..O......
 .............................
 .................OOO..O......
 ................OOOO..O......
 ................O.....O.OO...
 ................O.OOO...OOO.O
 .................O.O......O.O
 ................O.OOO...OOO.O
 ................O.....O.OO...
 ................OOOO..O......
 .................OOO..O......
 .......O..OO.................
 ......O...OO.....OOO.........
 .....OO......O.OOOOOOO.......
 .O...OO..O..OOO..OOOOO.......
 .O.......O......O.....O....O.
 OO..O....O..O.OO......O..OOO.
 .O.OO......O....O.....O..OO..
 .O.OO........................
 .O.OO......O....O.....O..OO..
 OO..O....O..O.OO......O..OOO.
 .O.......O......O.....O....O.
 .O...OO..O..OOO..OOOOO.......
 .....OO......O.OOOOOOO.......
 ......O...OO.....OOO.........
 .......O..OO.................

By combining the above small component with multiple copies of the "MWSS"
repeatable tagalong, a slow period 4 spaceship can be made which is as
wide and as long as desired. Therefore, like the period 2 and period 3
spaceships, a constant percentage of an arbitrarily large square can be
filled with a spaceship. How this can be done is shown below.

[Method for building long and wide slow period 4 spaceships (speed c/4)]
 ......OO............................................O...........
 ......OOOOOO.....................OOO..............O.............
 .....O...O.....OOOO.............OOOOOO...........O.....O........
 .OO.OO..O.OO.OO....OO.........OO.OOOOO..........O.......O.......
 OOOO....OOO..OO...........O...O.O.....O....O.O..O.OOOOO.O....O..
 O..O.....OOO..O......O.OO.O.OO........O..OOO.O.O..O....OOO.O.O..
 O.O............OO..O.O.O......OOO.....O..OO....OOO.........O.O..
 .O..O.O.........................................................
 O.O............OO..O.O.O......OOO.....O..OO....OOO.........O.O..
 O..O.....OOO..O......O.OO.O.OO........O..OOO.O.O..O....OOO.O.O..
 OOOO....OOO..OO...........O...O.O.....O....O.O..O.OOOOO.O....O..
 .OO.OO..O.OO.OO....OO.........OO.OOOOO..........O.......O.......
 .....O...O.....OOOO.............OOOOOO...........O.....O........
 ......OOOOOO.....................OOO..............O.............
 ......OO........................................................
 .................................OOO..O...........O..O..........
 ................................OOOO..O...........O..O.OO.......
 ................................O.....O.OO.......OO...OO..O.O...
 ................................O.OOO...OOO.O.....O.OOO..OO.O...
 .................................O.O......O.O.....O...........OO
 ................................O.OOO...OOO.O.....O.OOO..OO.O...
 ................................O.....O.OO.......OO...OO..O.O...
 ................................OOOO..O...........O..O.OO.......
 .................................OOO..O...........O..O..........
 ................................................................
 .................................OOO..O...........O..O..........
 ................................OOOO..O...........O..O.OO.......
 ................................O.....O.OO.......OO...OO..O.O...
 ................................O.OOO...OOO.O.....O.OOO..OO.O...
 .................................O.O......O.O.....O...........OO
 ................................O.OOO...OOO.O.....O.OOO..OO.O...
 ................................O.....O.OO.......OO...OO..O.O...
 ................................OOOO..O...........O..O.OO.......
 .................................OOO..O...........O..O..........
 ......OO........................................................
 ......OOOOOO.....................OOO..............O.............
 .....O...O.....OOOO.............OOOOOO...........O.....O........
 .OO.OO..O.OO.OO....OO.........OO.OOOOO..........O.......O.......
 OOOO....OOO..OO...........O...O.O.....O....O.O..O.OOOOO.O....O..
 O..O.....OOO..O......O.OO.O.OO........O..OOO.O.O..O....OOO.O.O..
 O.O............OO..O.O.O......OOO.....O..OO....OOO.........O.O..
 .O..O.O.........................................................
 O.O............OO..O.O.O......OOO.....O..OO....OOO.........O.O..
 O..O.....OOO..O......O.OO.O.OO........O..OOO.O.O..O....OOO.O.O..
 OOOO....OOO..OO...........O...O.O.....O....O.O..O.OOOOO.O....O..
 .OO.OO..O.OO.OO....OO.........OO.OOOOO..........O.......O.......
 .....O...O.....OOOO.............OOOOOO...........O.....O........
 ......OOOOOO.....................OOO..............O.............
 ......OO............................................O...........

The following is another connecting tagalong that bridges the gap between
the sparks of two slow period 4 spaceships. This tagalong was found by me,
and so is the only result since Dean Hickerson's earliest slow period 4
spaceship that was not found by Hartmut Holzwart. In the following, two
different spaceships provide the necessary sparks. The tagalong is nestled
very close to the upper spaceship, but still only reacts in a single place.

[Two period 4 spaceships with bridging tagalong (speed c/4)]
 .....................OO......O.......................
 ................OOO..OOO.............................
 ..................O..OO.O.O.....O....................
 ................OO.....OOO.......O...................
 ............OO..O..OOO.O...OOOOO.O....O..............
 ...........OO.OO.....O....OO....OOO.O.O..............
 ............O...O.........O.........O.O..............
 ...........OO...O....................................
 ............O...O.........O.........O.O..............
 ...........OO.OO.....O....OO....OOO.O.O..............
 ............OO..O..OOO.O...OOOOO.O....O..............
 ................OO.....OOO.......O...................
 ..................O..OO.O.O.....O...O.........O.O....
 ................OOO..OOO...........O.O.....OOOOOO..OO
 .....................OO......O....O.O....OOOO.....O..
 ...............................OO........OO.O.O......
 ..............................OO....O..O..O..........
 ....................................OOOOO............
 .............................OOOO....................
 ....................................OOOOO............
 ..........O...................OO....O..O..O..........
 ..........O...............OO...OO........OO.O.O......
 ......OO.O.OOO..........OO...O....O.O....OOOO.....O..
 O.OO.OO.OO..O.O...OO.OOOO..........O.O.....OOOOOO..OO
 O...OO..O.OO..OOO..O.OO..OO...O.....O.........O.O....
 O.OO....OOO.O.OOO......OO..O.........................
 ........OO.O...............O..O......................
 O.OO....OOO.O.OOO......OO..O.........................
 O...OO..O.OO..OOO..O.OO..OO...O......................
 O.OO.OO.OO..O.O...OO.OOOO............................
 ......OO.O.OOO..........OO...O.......................
 ..........O...............OO.........................
 ..........O..........................................

Very recently Hartmut found a period 4 spaceship with a completely new front
end. It still uses a pair of pre-traffic lights like one type of slow period
4 spaceships, but they are separated widely in this spaceship. The back end
of this spaceship is similar to other back ends, and so this spaceship can
support similar tagalongs.

[Period 4 spaceship (speed c/4)]
 ..O.OO...O.....................
 OO...O...O..OO....O............
 ..O.O...O....O..OO.............
 ......OOO..OO.OO..O............
 ......OOO...OOOOO.O..OOO.O.O...
 ........O.....O.O.OO..OOOO...O.
 .........OO......OO...........O
 .........OO.......OOOOOOOOOOO.O
 ...............................
 .........OO.......OOOOOOOOOOO.O
 .........OO......OO...........O
 ........O.....O.O.OO..OOOO...O.
 ......OOO...OOOOO.O..OOO.O.O...
 ......OOO..OO.OO..O............
 ..O.O...O....O..OO.............
 OO...O...O..OO....O............
 ..O.OO...O.....................

As has been seen in this article, the knowledge of c/4 period 4 spaceships
is very rudimentary, and only a couple of methods of constructing large
spaceships are known. The grammar for constructing such spaceships is
very simple, and only contains a couple of components. Therefore this
article has mostly been a catalog of sporadic results. (And so unlike
previous articles, essentially nothing that is known has been left out.)

This will also be true for the next article in this series, which will cover
the remaining class of period 4 spaceships. These are the ones which travel
at the "normal" speed of c/2. Some of these new spaceships require the
assistance of the standard LWSS, MWSS, or HWSS. But as you will see, this
will not be true in general.

That article should appear in about two weeks.

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