Complex sentence: The greater use of railways at the start of the 20th century meant that passenger numbers decreased until only a market day trip remained; this reduced service, using the steam packet "Celia", finally ceased during the First World War.
Split into simpler sentences: The greater use of railways at the start of the 20th century meant that passenger numbers decreased until only a market day trip remained. This reduced service, using the steam packet "Celia", finally ceased during the First World War.