transistor and switch comparison

In this circuit Lamp X1 is Switched by a transistor Q1 and Lamp X2 is switched by a mechanical switch S3. you will notice Q1 and S3 are in in similar positions with respect to the Lamps they control. However, the Transistors base terminal needs the correct electrical conditions to be met in order to switch on .Lets examine what those conditions are. 1: first check S1 , S2 and S3 all open R2 the 100K variable resistor should be at 0.00%