The remainder of this paragraph is in Captain Burslem's own words.
I am indebted for the knowledge of the existence of these caves to W.A. Sandford, Esq., F.G.S., who informed me that an account of them was to be found in a book of travels by an English officer. I am not aware that they have been visited on any other occasion than this.
Reise durch Island, Copenhagen, 1744 (being a German translation from the original Danish), i. 128 sqq.
Henderson's Iceland, ii. 189 sqq.
Pp. 145 sqq.