Delphine Rehm, age 13, of Lowell, Mass., for her question:

HOW LONG IS CANADA’S RIDEAU CANAL?

Rideau Canal is a Canadian waterway that connects the Ottawa River at Ottawa with Lake Ontario at Kingston. It is 123 miles long and has 47 locks, each 134 feet long, 33 feet wide and five feet deep. Eight of the locks are in Ottawa.

The Rideau Canal actually consists of the Rideau and Cataraqui rivers, several lakes and some short canals.

One branch of the canal, known as the Tay branch, extends to the town of Perth, and has two locks.

The Rideau Canal was completed a long time ago—in 1832. It was designed to offer a safe route for gunboats and military supplies between Montreal and the Greak Lakes.

Rideau is an important name in Ottawa. Rideau Hall, also called Government House, is the official residence of the Canadian governor general. It stands near the mouth of the Rideau River in Ottawa. Thomas McKay, a lumberman, built it in 1838. The Canadian government bought this gray limestone building in 1868 for Baron Monck, the first governor general. The home of the prime minister is nearby.