`` sir - his royal highness sent me here to secure the pass for his grace the duke of atholl and his convoy and if his grace should be obliged to pass this way it 's desired that in case you can not get boats sufficient to transport them , that you will cause build a bridge to facilitate their passage and it is apprehended the men-of-war and armed boats in the firth will endeavour to interrupt the passage here , it is not to be doubted but that there will be an attempt from stirling castle to cover their designs , for which you will use your best endeavour to keep them in , by drawing some of your troops that way to make a diversion .