It's amazing that something only an atom thick can be an impenetrable barrier. You can have gas on one side and vacuum or liquid on the other, and with a wall only one atom thick, nothing would go through it.
To grieve at any loss, be it of friend or property, weakens mind and body. It is no help to the friend grieved for. It is rather an injury; for our sad thought must reach the person, even if passed to another condition of existence, and it is a source of pain to that person.