From the 1968 lecture programme:
The lands Gulliver visited were technologically underdeveloped. He saw no steam engine nor even gunpowder. What does scale mean for the engineer, for all the man-made things of our modern world? We will look at ships and guns and chemical plants, at transformer sub-stations and computers, and try to see what our technology would have been like had we humans been the size of the men of Gulliver's voayges. For example, Brobdingnag turns out to be a very peacable land, until lately at least, for its big cannon would have impratically small range; Lilliput, on the other hand, was at once horribly affetced by the introduction of gunpowder. Each development has its proper size. Model makers will recognize some of these results out of their own ecxperience. Large-scale engineering is still undeveleoped among us for such reasons.
Please note: The Ri has removed footage of various man propelled flying machines as the third party copyright could not be cleared.