Complex sentence: In May 1850, the first preparations were begun on Manzanillo Island, and the start of the roadway was partially cleared of trees and jungle on the mainland; but very quickly, the difficulty of the scheme became apparent.
Split into simpler sentences: In May 1850, the first preparations were begun on Manzanillo Island, and the start of the roadway was partially cleared of trees and jungle on the mainland. Very quickly, the difficulty of the scheme became apparent.