The Middle Jurassic of Yorkshire consists of non-marine strata, known collectively as the Estuarine Series, and several intercalated marine bands. The non-marine beds have the characteristics of deposits formed as a delta rather than in an estuary, and are, in fact, strongly reminiscent of the Coal Measures in their general appearance. In the coast section, where they are admirable exposed, which are usually due to the presence of false bedded sediments replacing the normally parallel bedded strata. Thick wedges of sandstone replacing the Dogger, and sometimes part of the Upper Lias too, have been described by Dr. Rastall and Fox-Strangways. They are particularly noticeable when they interrupt the top seam (i.e. the Dogger) in the iron mines, where they are called “freestone baulks” by the miners. The same phenomenon is better known in the Coal Measures, where the term “washout” is used for a mass of sandstone suddenly replacing coal. Although there are several objections to the term “washout”, it is used here since it had become so well established in Coal Measures geology.