Doris Kinney, age 13, of Rockford, Ill., for her question:

HOW LONG IS THE MOFFAT TUNNEL?

Moffat Tunnel in Colorado is one of the longest railroad tunnels in the world. It slices its way through James Peak in Colorado for a total of 6.23 miles.

Moffat Tunnel is made up of two separate tubes. The largest is 16 by 24 feet and it is used for trains. The second tube, or bore, is 8 feet by 8 feet and carries water from the Fraser River to Denver.

The tunnel was drilled through rock from each side of the Continental Divide at an elevation of 9,200 feet. The tunnel shortened the distance between Salt Lake City and Denver by 176 miles.

By using the Moffat Tunnel, trains avoid snowstorms, snowslides and steep grades.

The tunnel was named for David H. Moffat, an American railroad builder and banker. It was leased to the Denver and Salt Lake Railroad.