Abstract: In an exemplary embodiment an ultrasonic head comprises at least one transducer element which, possibly via a liquid precursory path, transmits ultrasonic signals and receives echo signals. It is the object of the disclosure to design the applicator such that it is simply and rapidly adjustable to variable depth scanning. In accordance with the disclosure this object is achieved in that the liquid precursory path has the form of a sack, containing the liquid, which sack is capable of being coupled with the transducer element or elements on the ultrasonic head in the manner of a spacer by a readily detachable mounting arrangement.

Abstract: A method and apparatus for calcining minerals, particularly limestone, in a shaft kiln having at least two vertically spaced levels including cooled hollow supports through which a solid fuel is introduced into the kiln. One feature of the present invention resides in employing a granular coal as the fuel while other features are involved with the distribution of fuel between various inlet points, suspension of the fuel in an airstream, and the mechanical construction of the fuel conduits and their support located within the shaft kiln.