Jon is right here Potato. The invisible hand has nothing to do with supply or demand. The invisible hand are just the invisible forces that make people behave a certain way...

Before you tell Jon'C about the concepts of supply and demand, just notice that when drawing a simple supply and demand graph, you always have to add too it to represent an externality. That by its definition assumes that sometimes markets don't adjust for what we deem are negative externalities. One might argue that "Well, a free market would adjust and you could always just contract everything!", but the transaction costs of this are sometimes so high that it leads to greater inefficiency to make things even clearer. For more on that, check out Normative Coase vs Normative Hobbes.