Tiger, are you sure that's the order of the verses as Tom wrote them? PP&M leave out the subway verse but end with the "...lie in my bed in the morning..." verse. RUS has all 4 verses and also ends with that verse, but has the "...subway..." verse 3rd. I thought the correct order was
• "...lesson too late..."
• "...subway rumbling..."
• "...reasons aplenty..."
• "...lie in my bed..."

Any definitive answers? [Not that folks won't sing 'em in whatever order they darn well please, anyway, mind you...]

Genie

PS, re the "made of sand" allusion, I always connected it with sand castles and sand sculptures at the beach [ephemeral] or with the Biblical parable of the wise man building his house on the rock and the foolish man building his house on the sand [unstable, precarious].