A little history of infrastructure. かつて ('once, formerly, long ago') is a formal adverb meaning 'in the past' — used especially for historical narration. 曳く ('to pull, to drag') is a slightly literary/technical verb for pulling a vehicle or cargo, sometimes written 引く or 牽く depending on context. により (the formal version of によって) marks the cause or means — 'by means of the invention.' The tense seam is worth noting: the first clause is past (曳いていた), and the second is also past (現れた), with 'by the invention' acting as a causal bridge.