Gandalf's Wand!
This is one of the few (the only?) pictures of Gandalf 'in action' by Tolkien.
Its not too easy to make out here, but he seems to have a wand, as opposed to a staff, going by the way he's holding the thing. He's clearly grasping it by the end, & its simply not long enough to be a staff. Yet its clearly stated in Ch1 of TH that Gandalf had a staff.
Does this illustration show the 'official' method of using a staff? Did Gandalf also have a wand concealed under his cloak, or did Tolkien just forget himself for a moment?
The other interesting question is what exactly Gandalf is using the wand/staff for at that point? Is he 'helping' the effect of the sun on the trolls, is he showing Arien exactly where the trolls are, so she can focus her powers on them, or what?
What we seem to have is the only illustration of Gandalf doing magic, at a time when he doesn't actually need to do anything at all....
(I particularly like the 'Doh!!!' look on the middle troll's face, btw)