In the month of May, 1856, H. M. Lords Commissioners of the Admiralty, advised by the Astronomer Royal, were pleased to entrust me with a scientific mission to-the Peak of Teneriffe. Their Lordships most liberally placed 500l. at my disposal for defraying the necessary expenses; and left me, within bounds of such expenditure, as untrammelled by detailed instructions, as any explorer could desire.

No sooner was the authorization known, than numerous and valuable instruments were kindly proffered by many friends of astronomy; and one of these gentlemen, Robert Stephenson, M.P.,—who had indeed fully appreciated the scientific question in 1855, and even asked me to accompany him to the Canaries in that year,—immediately offered the use of his yacht “Titania;” and by this, greatly ensured the prosperity of the undertaking.

The object mainly proposed, was, to ascertain how far astronomical observation can be improved, by eliminating the lower third part of the atmosphere. For the accomplishment of this purpose, an equatorial telescope and other apparatus were conveyed in the yacht to Teneriffe, in June and July 1856. There—with the approval of the Spanish authorities, (always ready in that island to favour the pursuits of scientific men of any and every country), the instruments were carried up the volcanic flanks of the mountain, to vertical heights of 8900, and 10,700 feet, and were observed with during two months.