The aim of the work was modelling of shaft and calculation of natural vibration frequencies and critical rotations of a large-size, vertical mixed flow pump of total length l=4866 mm. Equations of motion were determined analytically, and then calculation results were verified by numerical modelling. The difficulty of the problem consisted in the shaft bearing, in which four hydrodynamic bearings of unknown parameters were applied. A four-mass beam supported on flexible supports of rigidity k and damping c was assumed as the discrete model of the shaft. Equations of motion for the system were derived with the method of forces. In order to verify correctness of the derived equations, one considered three models of the beam with different support configuration: the beam supported on rigid supports, the beam supported on elastic supports, and the beam supported on flexible supports of rigidity k and damping c. Calculation results are presented in tables and graphs.

This article contains a bilingual, Latin-Polish, edition of a letter written by Erasmus to John Sixtin (Ioannes Sixtinus), a Frisian student he met in England. In it Erasmus describes a dinner party at Oxford to which he was invited as an acclaimed poet. In the presence of John Colet, leader of English humanists, table talk turned into learned conversation. Erasmus’s contribution to the debate was an improvised fable (fabula) about Cain who, in order to become farmer, persuades the angel guarding Paradise to bring him some seeds from the Garden of Eden. His speech, a showpiece of rhetorical artfulness disguising a string of lies and spurious argument, is so effective that the angel decides to steal the seeds and thus betray God’s trust. Seen in the context of contemporary surge of interest in the art of rhetoric, Erasmus’ apocryphal spoof is an eloquent demonstration of the heuristic value of mythopoeia and the irresistible power of rhetoric.