Shabbat 47: Insulation and the Transfer of Heat on Shabbat

We are permitted to carry our children, even if they are carrying stones (which are not to be carried on Shabbat).  Are small items insignificant and thus not worthy of consideration when it comes to measuring what is being carried?  A small item might mean nothing to a rich person, and so it might be permitted for them to carry it (like a tiny piece of frankincense on a coal pan which are nullified by the ashes).  But to a poor person, that frankincense could be used and thus it is significant; we should not move it on Shabbat.  Many other examples are provided - one item might look like another and thus it is prohibited to carry it on Shabbat.  Different consequences are faced depending on the transgression, as well.  

We are introduced to a new Mishna in amud (b).  It teaches that we are permitted to place vessels beneath oil lamps to catch any burning sparks that fall from the lamp to protect from a potential fire.  We cannot put water into the vessel because we would then extinguish the sparks, which is not permitted on Shabbat.  The Gemara immediately counters this logic: if we prepare the vessel to receive sparks aren't we putting the vessel in a "set aside" state?  Rav Huna, son a Rav Yehoshua says that the sparks have no substance.  The burn right away and leave no trace of oil in the vessel thus the vessel may still be moved.  

We then begin Perek IV where we move to discussions about transferring heat.  If a pot is removed from the fire on erev Shabbat, it may be insulted in materials that preserve but not increase its heat.  Raising the pot's temperature is like cooking.   Our new Mishna states that we may not insulate a pot of cook food on erev Shabbat with the solid residue of produce that has been pressed, nor in manure, salt, lime, nor sand whether moist or dry.  We cannot insulate a pot in straw, the residue of grapes, soft materials from clothing, grass or other moist materials.   These may insulate a pot when they are dry.

Tbe rabbis discuss different foods and how much heat they release.