The majority of those engaged in this physical exploration of caves are French. France possesses a Société de Spéléologie, the secretary of which, Monsieur E. A. Martel, author of _Les Abîmes_, is a most indefatigable and courageous explorer, and the man who has made the science an important and a living one. But M. Martel himself awards the title of "créateur de la spéléologie" to a forgotten predecessor, Dr. Adolphe Schmidl, who published _Die Grotten und Höhlen von Adelsberg_, in 1854. In this country, although such brilliant discoveries have been made of extinct animals and prehistoric relics of humanity, cave exploring of this kind is a new pursuit. M. Martel says, in _Irlande et Cavernes Anglaises_, 1897: "In short, the underground of the calcareous regions of the British Isles may be considered as being, topographically, very insufficiently known; this is the conviction impressed on me by my own researches in 1893." Something has been accomplished since that date. Two or three clubs, consisting chiefly of climbers, and a few speleologists working independently, have effected a thorough examination of the great caverns of the Peak, the extraordinary system of underground waters, huge cavities, and profound abysses in the West Riding, and the beautiful caverns of Somerset. But the ground that remains unexplored, the opportunities for adventure and the possibilities of discovery are such as may probably astonish those people who think there is nothing of the sort left in Old England.
Caves are formed in calcareous strata by the chemical action of water laden with carbonic acid, and by the mechanical action of streams. In consequence of the original structure of the Limestone, the joints of which run at right angles to the bedding planes, these eroded hollows have two dominant forms: the vertical pot, swallet, or hole, produced by the widening of a master-joint; and the horizontal water-channel, running in the same direction as the line of stratification. But the strata being commonly tilted, these pits and abysses are often a long way out of the vertical, and the caverns that follow the strata very steep. Many of these ancient watercourses are now dry, but others are still traversed by streams, and present the explorer with most formidable obstacles. The complete exploration of any cave system would involve the tracing out of all its passages from the point where the stream or streams enter the earth to the point of exit. But I know not a single instance where such a task has been worked out in its entirety. In many cases the streams enter the ground merely as small rivulets, and begin to excavate passages practicable to man only at a considerable depth. "Siphons," or traps, as they ought to be called, complete or partial chokes, and a variety of other causes, may put insuperable obstacles in the explorer's way.