26 Book of Locomotives 

 Whyte, introduced the mode of expressing 

 the wheel formula by figures. The system 

 now bears its inventor's name, and is exten- 

 sively used. Whyte says that you must 

 reckon upon an engine having three sets 

 of wheels, viz., leading, driving and trailing. 

 If any of the sets are not used, we must 

 use an o. For example, the usual type of 

 goods engine has six-coupled wheels. To 

 express this Whyte uses the figures O-6-O. 

 For the " Atlantic " type of express engine 

 it becomes 4-4-2, which means, four leading 

 wheels, that is a leading bogie, four driving 

 wheels coupled together, and a pair of 

 trailing wheels under the huge fire-box. 



The single-drivers were the most graceful 

 of all locomotives ; because their weight was 

 limited it was possible to make them grace- 

 ful, and their big single driving wheels 

 gave them a most majestic look. How they 

 ran! The Midland drivers called theirs the 

 " spinners ", because they travelled so 

 quickly and with so little punching the 

 latter meaning that the movement was regu- 

 lar and the engine steady. 



