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Aht. XI. An Account of a Barometrical Measurement of 

 the Height of the Pico Ruivo, in the Island of Madeira. 

 Extracted from a Letter written % Captain Edward 

 Sabine, of the Royal Artillery, to Sir Humphry 

 Davy, Bart., President of the Royal Society, dated in 

 January, 1822, on board his Majesty's Ship Iphigenia, 

 on passage between the Cape Verd Islands and Goree: 



" You are probably aware that the mountainous parts of 

 the interior of Madeira have been rendered accessible to a 

 greater distance than formerly, by roads of recent construction, 

 passable at most seasons by mules, or by the small horses of 

 the island, which vie with mules in the sureness of their foot- 

 ing. I availed myself of the opportunity which our short stay 

 afforded, of making an excursion to the summit of the Pico 

 Ruivo, the highest of the island, with a view to obtain a mea- 

 surement of its height, and to make a first essay with a portable 

 barometer having an iron cistern, on which Mr. Newman had 

 bestowed much pains, to obviate the liability to the various 

 errors to which these instruments are generally subject. The 

 party consisted of Captain Clavering, of his Majesty's ship 

 Pheasant, Mr. Whitelaw, surgeon of the Iphig-enia, Mr. George 

 Don, naturalist of the Horticultural Society, and two mid- 

 shipmen of the frigate ; we were accompanied by Mr. Black- 

 burne, an English merchant resident at Madeira, who, having 

 before ascended the Peak, was kind enough to undertake to 

 conduct us, and by his local knowledge and authority over ouf 

 Portuguese attendants and guides, as well as by his own enter- 

 prising spirit, enabled us finally to accomplish our purpose. 

 Lieutenant Stokes, of the Iphigenia, was so kind as to remain 

 on board the frigate throughout the day, to note the variations 

 in temperature and density of the atmosphere, and of the point 

 of deposition indicated by Mr. Daniell's hygrometer. These 

 were obsci-ved hourly by a chronometer, so as to be simultane- 

 ons with others which we should make at the heights at which 

 we might find ourselves. I shall detail the observations, and 



