I wrote:

In this Plain Course of Bob Doubles we have rung 40 changes. On 5 bells
there are 120 (= 2x3x4x5) possible combinations. To reach these other
combinations we will have to introduce further variations to the Plain
Course, and we do this by calling Bobs.

And so to Bobs.

The result of a Bob is to switch the bells around so that they are in
yet another order, and can continue in a new course in this modified
order, resulting in a different set of changes being rung. To ring a
full extent of Plain Bob Doubles -- 120 changes known as a 120 (said as
a 'one-twenty') -- we must call three Bobs to ring three different
courses of 40 changes each.

In Plain Bob, a Bob is called to take effect at the point where the
bells (other than the treble which in this method is always plain
hunting) are about to dodge or make 2nds or 4 blows behind (the latter
also known as 'long 4ths'). This always occurs as the treble is leading.

The Bob causes this to happen:

 if you were about to ring 4 blows behind: then you are unaffected --
 ring 4 blows behind as expected; and next time you will dodge 3/4 up as
 expected

 if you were about to make 2nds: then instead, carry on plain hunting
 up to the back ('run out'); you will make 2nds next time instead --
 effectively you have moved back one place in the cycle of work

 if you were about to dodge 3/4 down: then instead, carry on hunting
 down to the lead ('run in'); you will dodge 3/4 down next time --
 effectively you have moved back one place in the cycle of work

 if you were about to dodge 3/4 up; then, you are already in 4th
 place, so ring an extra blow in fourth place (i.e. 'make 4ths'), and
 turn round and hunt down to the lead; next time you will ring 4 blows
 at the back; this bell is said to 'make the bob' -- effectively you
 have moved *two* places back in the cycle of work. Effectively you
 have taken the place of the bell that would have dodged 3/4 down.

What does this look like in the now-familiar diagram? Here, first is a
normal dodge in Bob Doubles, the first you get to in a plain course, and
which we have already seen:

35142
31524
13254 -- bell 2: dodge 3/4 down; bell 3: make 2nd's;
         bell 4: 4 blows behind; bell 5: dodge 3/4 up
13524 -- continue plain hunting from this new position
31254

If the conductor wishes to vary this then they will call 'Bob!'  at
the start of this section, and at the next handstroke as the treble
leads the other bells will perform the 'bob' action rather than the
usual dodge:

35142 -- 'Bob!'
31524
13254 -- bell 2: run in to lead; bell 3: run out to back;
         bell 4: 4 blows behind: bell 5: make the bob
12354 -- continue plain hunting from this new position
21534
25143
52413
54231
45321
43512
34152
31425 -- get ready to dodge as normal (unless another bob is called)
13245 -- bell 2: dodge 3/4 down; bell 3: make 2nds
         bell 4: dodge 3/4 up;   bell 5: 4 blows behind
13425 -- continue plain hunting from this new position
31245
32154

So, nice and easy. You just have to remember all this in addition to
the normal work. Each time, as you plain hunt between the dodges (while
carefully counting your place -- thinking '3rd, 2nd, lead, lead, 2nd,
3rd, 4th' etc as you make each stroke) ... all the time whilst doing
this plain hunting you also have to think 'next time I make 2nds' or
'next  time dodge 3/4 up' or whatever; and you have to think 'but if a
Bob is called, run out and make 2nds next time' or 'if a Bob is called
make 3rds and do 4 blows in 5th next time' and so on.

How do we use this to ring a 120, the full extent of 5 bells? We can
call bobs in a number of different places, though always as the treble
is about to lead and the other bells about to dodge. The different
locations affect the other bells in different ways. We might choose to
call a bob when bell 4 is about to do its 4 blows behind. It will be
unaffected by the bob, and we can ring a whole course in this new
order. Then just as it is about to do 4 blows behind again (40 changes
later) we can call another bob to get a different order. Then ring
another course of 40 changes, and once again as 4 gets to ring 4 blows
behind we call a third bob. 4 is again unaffected, and this third bob
brings the bells back into a plain course and almost immediately to
rounds.

This is a very simple touch to call, probably the first that a
novice conductor will attempt (and I have never called a touch of
anything yet, at least partly because my band of ringers are not all
able to ring a touch as yet). One advantage of it is that one bell is
entirely unaffected by the bobs -- which means that it can be rung
with a novice ringing that bell, or perhaps with the novice conductor
ringing it so that they can concentrate on one thing rather than two.

In our next lesson :-) we will extend Bob Doubles (rung on 5 bells) to
Bob Minor (on 6) and Bob Major (on 8). For a plain course, and for a
simple touch, these are trivial changes in theory. Then we will take a
look at Grandsire Triples (rung on 7 bells), which forms the chapter
themes of a large part of NINE.

simon