The author referred, in the first instance, to the character of stratification, illustrating the subject by specimens displaying the intermittent character of the carrying agent and of the supply of material, pointing out the Hailes Quarry as furnishing the best example in the neighbourhood of the repetitions of strata. He then stated the views of Townson, Whitehurst, and Jameson, as to the relation of the trap rocks to the sandstones with which they are interstratified. He then took notice of a statement in vol. xiii. of the Transactions of the Society, recorded by Lord Greenock, that Edinburgh may be considered as a valley of elevation, the trap rocks in the neighbourhood dipping outwards as from a common centre.