log flume vs water slide

log flume

noun
  • An amusement park ride where passengers sit in a hollow log and travel along a track or circuit powered mostly by the flow of water. 

  • A flume specifically constructed to transport lumber and logs down mountainous terrain to a sawmill by using flowing water. 

water slide

noun
  • A recreational slide with water flowing down it to reduce friction, sometimes involving the participant sitting on a mat or raft and sometimes leading into a pool at the bottom. 

How often have the words log flume and water slide occurred in a corpus of books? (source: Google Ngram Viewer )