The name on each of the other steam locomotives shows that it belongs to
a type that has a particular arrangement of wheels. All Pacific-type
engines have four small wheels in front, then six big ones, then two
small ones in back. Mikados have two small, eight big, then two small
ones. The way to write these wheel arrangements is 4-6-2 and 2-8-2. If
an engine is called a 2-6-0, that means it doesn’t have any small wheels
at the back. A 2-8-8-2 has two sets of big wheels and two sets of small
ones. And 0-8-8-0 means there are no small wheels at all.
[Illustration: UNION PACIFIC NORTHERN