Is the reason in here (yard, engine stall/roundhouse areas) that tracks are right even with the soil/earth around it due to track (ties) originally laid right on ground ? Or, is mostly all track laid on 2-3 foot deep ballast but the soil is built up around it to make it easier for switch crews to get to ground throws/couplers and walk cross many tracks ? Is it simply erosion out in countryside were tracks are in weeds, yet it's on (now hidden) deep roadbed ? Or, is it, again, simply laid on little or no ballast to begin with when it's a say, 50 lb.-rail spur out in the woods ? Those 1860s photos of track do look right on the ground allot, at ends of lines especially....Did it just continue this way but replacing ties and changed to heavier rail over the decades ?