Abstract: .[.A method and at least one mechanism for carrying out the method is disclosed. A method of (1) generating time modulated torque pulses by engaging and disengaging a mud turbine driven rotating torque generator in the bottom of a wellbore, and (2) monitoring the top of the drill string for the torque pulses therein may be practiced by a mud driven turbine inertial wheel for being momentarily and precisely braked or decelerated relative to a drill collar on the lower end of a drill string in a wellbore while drilling for generating the time modulated torque pulses in the drill string for being monitored at the surface. Mechanical, electrical, and fluid operated brakes and a mud turbine driven motor are disclosed for providing power to a motor at the bottom of the drill string or for being intermittently braked rapidly for generating the torque pulses..]. .Iadd.Methods and apparatuses for driving a means, as a power generator in a drill string while drilling, in a well are disclosed.