To use X-ray in Eaglercraft 1.8.8, you need a resource pack that makes common blocks (stone, dirt, gravel) transparent while leaving ores visible.
When you load XRay 188 in Eaglercraft, your GPU renders the world as a hollow shell. All you see are floating ores, exposed dungeons, and the dark outlines of abandoned mineshafts. Diamonds that would take an hour of branch-mining to find become visible from 50 blocks away. xray texture pack 188 eaglercraft