Abstract: The invention has for its object a device for measuring the slope parameters of a material contained in a cylinder rotated around the axis thereof.This device, which senses radiations generated by radio-isotopes passing through the cylinder and the material contained therein, comprises means 1 generating the said radiations and means 8a, 8b picking up the latter fitted outside the cylinder in such a manner that, during the rotation thereof, the radiation generated by the radio-isotopes passing through the slope of material 5 in at least two separate locations is sensed in a specific point of the cylinder, as well as means for analyzing the signals received by the means sensing said radiation.This device is to be used together with a rotating furnace and particularly a cement kiln.