Andy - If you want to make another dibber from the green logs, split one down the middle and if it's big enough split one half again. If you carve a dibber from this quarter it should not split when it dries out.
Cleaving or splitting wood along the grain when it is unseasoned (just cut)...is an age-old technique which frees up the natural stresses within the wood preventing it from splitting later. By cleaving it you are actually following the lines of natural stress and releasing them so the surrounding wood is less likely to split later.
Some woods are more prone to splitting when drying out too quickly...some are ideal for using like this ....green.
If you take your logs and split them with a splitting axe or wedge to roughly the size you need...like quartered...you can then stack them in the dry outside...away from direct sunshine and large temperature variations...stack them on "sticks"..small pieces of wood which will allow the air all around them. Woods prone to splitting can be further prevented from doing so by waxing the ends. I have a biscuit tin which I stick on the stove and melt candles in and then I dip the ends in that...it's cheap and cheerful and works.
There is a wealth of green woodworking and seasoning information on the Internet...just Google it.
As Chris says...an axe and froe are great tools...look out for them at bootfairs...this Ward and Payne one was a couple of quid if that...I forget...
...and can be honed to a super sharp edge that shaves hairs!
Thanks all for all that, I have learnt something there.
I have some Holly just cut down which I think is prone to splitting but will collect it and "start" using the chainsaw I got
the other day! and stack it, I was told pva glue on the ends would do.