_London, October 6th._--I left Dunrobin after breakfast on Saturday morning, 3rd inst., and arrived in London on Monday (yesterday) at 11 A.M. My journey was after this wise: We (i.e. Mr. Marshall of the Life Guards, an aide-de-camp of Lord Carlisle's, who travelled from Dunrobin with me) got into the mail at Golspie and took our places to Inverness. At Tain, the first stage, we walked on, leaving the coach to overtake us. After walking three miles, and no coach coming, we got alarmed, and on enquiry of the first man we fell in with, found we had come the wrong way, and that the mail had gone on. We started on our return to Tain, and falling in with a good Samaritan in the shape of a banker in that place, who was driving in the opposite direction, he took us up in his gig, and drove us back to the inn, where we took post, and followed the mail to Inverness, where we arrived an hour after it. There we slept, and at five minutes before five on Sunday morning we were in the mail again, and arrived at Perth at six o'clock, making 117 miles in thirteen hours. In twenty minutes more we were in the mail train, and reached Euston Square safe and sound at eleven o'clock, doing the distance between Perth and London in seventeen and a half hours. I have seen a vast deal of very beautiful scenery of all sorts, but the most beautiful of all (and I never saw anything more lovely anywhere) is the road from Blair Athol to Dunkeld, which includes the pass of Killiecrankie. [Sidenote: REINFORCEMENTS FOR INDIA.]