also a sensor s this sensor and its associated circuitry is one of the standard sensors used in mwd for example an inclinometer it functions in addition to the sonic logging apparatus which is the subject of this invention i e by well known procedures of multiplexing the apparatus shown in fig1 is designed to produce a regular mwd log of for example inclination using the valve 1 2 for telecommunicating inclination data to the surface by means of the pulses generated by the valve 1 2 and at the same time use the pulses from the valve 1 2 to produce the signals needed for the sonic log the entire system is maintained in synchronism by the electric 34 clock 34 31 fig4 shows an additional device a 34 restrictor 34 that can be placed in the mud circuit below the tool of fig1 and the bottom of the well i e the bit the purpose of this restrictor is to increase the pressure differential between the inside of the collar and the annulus since sometimes in modern drilling methods very low differential pressures and high flows are employed in reference to fig4 indicates the special restrictor sub and in its interior is a non erodible insert 43 such as tungsten carbide bit nozzle as manufactured by dresser industries inc of dallas tex u s a it must be pointed out that the sonic barriers r of fig1 may sometimes be difficult to install and also the separation between the 34 sound source 34 of the valve 1 2 and the detectors 6 and 7 may sometimes be required to be of substantial length in such cases it may be necessary to provide separate housings for the detectors 6 and 7.