FIG. 1 is a top perspective view of a slide lamp showing our new design; FIG. 2 is a bottom perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a left side view thereof, the right side being a mirror image; FIG. 6 is a top view thereof; and, FIG. 7 is a bottom view thereof. The broken line disclosure represents portions of the lamp which form no part of the claimed design.