The books I own and many internet sources give exactly the melody of the MIDI file posted here. Many others don't give any melody, but assert that it's a two part round. Therefore I think that this has always been the standard version.

The version in four parts linked above I found in one other place only, in C major. In my opinion, it's clearly apocryphal. Since the four lines of the text form a tight unit, the desire for such an extention is quite understandable. So it may not be too much of a sacrilege that I propose one of my own making, much easier to sing and sounding better, I hope:

X: 3
T: White Coral Bells 3.0
C: trad.-to-be, Ceto
M: C
L: 1/4
K: C
c2  B A | G3    E | F A G F | E4     |
C E D F | E G c e | d2  B2  | c4     |
G3    z | c B A G | z F2  D | G A G2 |
E z G z | C D E G | A c d G | c4     |

(For the closing fermata, add a C4 ad lib.)

Would the first group of Girl Scouts to try this out at the campfire please post their opinion here ;-).

Ceto