Who knows what 'shot rock' is? Not very many of us I suppose :). Once the solid granite was blasted away to make a hole for the new cottage foundations, you can appreciate that nothing is level and the whole surface is pretty jagged and mushy. That's where shot rock comes in.
Shot rock is dumped in to the bottom of the hole and spread evenly everywhere. Then it's tamped down to compress it. The big value of compressed shot rock is that it provides a very secure, solid base for the foundations and it's permeable so that ground water perculates right through it and is transferred away from the lower level of the cottage.
