[This page][1] has a depiction of a wizard from a late 19th century [lantern slide][2]:

![enter image description here][3]

It sort of seems like this guy is somewhere between the modern Merlin/Gandalf vision of a wizard and older depictions of the "renaissance magus" like the one shown [here][4] of Dr. Faustus from a 1620 edition of *Faust*:

![enter image description here][5]

And [here][6] is an illustration of Merlin by Gustave Doré from 1868, you can see the image of the wizard already included the robes and the long white beard but perhaps the conical hat wasn't yet part of standard wizard regalia in the public imagination:

![enter image description here][7]

I would guess that "The Sorceror's Apprentice" from Disney's *Fantasia* helped cement the modern iconic image of a wizard's hat (in the same way *Wizard of Oz* cemented the image of a witch, inventing the notion that they had green skin for example). In this cartoon, Mickey gained temporary magic powers from "borrowing" the hat of his wizard master, which was pointed, blue, and had the star-and-crescent moon pattern often seen in later images of wizards. *Fantasia* came out in 1940, only 3 years after *The Hobbit*, so I don't know how likely it is that the Disney animators were influenced by Gandalf.

![enter image description here][8]


  [1]: http://museumvictoria.com.au/collections/items/750222/lantern-slide-wizard-cauldron-1850-1900
  [2]: http://memory.loc.gov/ammem/collections/landscape/lanternhistory.html
  [3]: https://i.sstatic.net/MnG1t.jpg
  [4]: https://olneytempest.wordpress.com/shakespeares-sources/prosperos-so-potent-art/
  [5]: https://i.sstatic.net/XyYe1.gif
  [6]: http://en.wikipedia.org/wiki/Lady_of_the_Lake#Later_uses
  [7]: https://i.sstatic.net/80DE1.jpg
  [8]: https://i.sstatic.net/QP2xM.jpg