The doctor, moreover, had written, in his spare moments, a valuable book on Edinburgh, and there was nothing that Donald enjoyed more than to spend his holidays tramping with his father through old and new Edinburgh. Edinburgh, you must know, was the capital of Scotland in the old days, and virtually is so to-day, and one of the most beautiful cities in the world. Donald knew most of the "sights" of the town as well as the doctor himself, but to the lassies all these marvels were much more of a novelty. It was a gay little party that got off an electric car (the Scotch call it "electric," as do the Americans, and not a "tram," as do their English cousins just over the border), Doctor Gordon leading the way, with a niece on either side of him, and the boys walking before. "Let us go to the castle first," said Don, who rather thought that he ought to help his father do the honours. "I don't believe Marjorie and Janet have ever seen it really well. You know, father, you always tell me something new about it every time we go there," said Donald, eagerly. So they crossed Princes Street Gardens, which divide Edinburgh into the "Old Town" and the "New Town." The "Old Town" is on a high hill, and on the highest part of all is Edinburgh Castle. It was not long before our party found themselves before its grand old walls. "Don, there is your favourite Highland Regiment coming out of the castle now," said the doctor. "Oh! they are going to drill; can't we stay and watch them awhile?" cried all the children, as with one voice. I know that American children would think the Scotch regiments the most picturesque soldiers in the world, in their old-time Highland costume. Here is a picture of the piper, playing on the Scotch bagpipes, so you can see for yourself what a wonderful uniform it is. [Illustration: THE HIGHLAND PIPER.] His kilt and stockings are made of the tartan which shows the Clan to which he belongs. In the olden time, each one of the great families of Scotland banded itself together, with its followers, into a Clan for protection, and thus each Clan was really a little kingdom and army in itself. The piper's plaid, which is a sort of shawl, is pinned on his shoulder with a great silver brooch. In this brooch is set a "cairngorm" stone, which is the yellow stone called a topaz; the national stone of Scotland, one might call it, as it is found there in great quantities. That funny-looking bag which hangs in front of him is called a "sporran," and by his side is a short sword called a "claymore," and in the olden time there was thrust into the stocking a dagger called a "skean-dhu." Would you not think he would be cold, with his knees bared to the cold east wind which blows over the castle high up on its rock? But no such thing ever enters his head, for Scotch children from infancy are used to going about with bare knees, winter and summer alike.