Which preposition to use with frustums

of Occurrences 1%

A.There are screws which profess to counteract the centrifugal velocity given to the water by imparting to it an equal centripetal force, the consequence of which will be, that the water projected backward by the screw, instead of taking the form of the frustum of a cone, with its small end next the screw, will take the form of a cylinder.

Which preposition to use with  frustums