level of the upper part of the tank 10 and the other considerably longer referenced 29 ends above a rotary sampler device designed as a whole by the reference 30 and fixed at the bottom of the vertical column 5 of the gantry 1 furthermore the filter 13 has an output valve or shutter 32 at its lower extremity for emptying the micro fines recovered from the filter which fall through a lower oblique tube 33 into a bag represented schematically and referenced 34 which quantity of fine material recovered per sample should not exceed 10 of the weight of the latter provision is also made at a suitable position on the side of the vertical column 5 of the gantry 1 for an electrical command desk 40 enabling the use of the whole of the gantry 1 and of its various equipments in an entirely automatic manner as can also be seen the manholes 21 of the tank 10 include covers referenced 35 which can be opened automatically by means of jacks 36 fixed on the tank and coupled to the pneumatic control circuit of the vehicle 11 before describing in a detailed way the functioning of this device and the putting into operation of the associated automatic sampling process it will be noticed that when the change over arrangement 27 is switched to the position permitting passage into the transfer tube 28 and during the descent of the probe 8 the product sucked up by the probe 8 arriving by the tube 15 in the receiver 9 is re cycled on the top of the tank 10 the purpose of which is.