496 Prof. Piazzi Smyth's Account of the [March 5 



vations, as those of solar and lunar radiation. But time fails me to 

 tell of two months' mountain experience of days, always better for 

 astronomy than in the towns below, and sometimes supremely 

 adapted therefor ; and of how, accompanied by two of the sturdy 

 seamen of the Titania, we tried our telescopes on the flanks of the 

 Peak itself, at a height of 10,700 feet, ascertained at once the 

 practicability and advisableness of greater heights still, and climbed 

 the culminating point of the mountain 12,198 feet high. 



To describe these operations in full, there is now neither time, 

 nor perhaps necessity, as the original observations, with all the nume- 

 rical and instrumental particulars, have been communicated to the 

 Admiralty, and by them were transmitted to the Royal Society, for 

 publication, in June last ; while as to the more popular part of our 

 daily experiences and little personal adventures, should any one 

 care to read them, are they not contained in a little book, recently 

 published by Mr. Lovell Reeve, and illustrated with genuine 

 photo-stereographs ? 



Such plates being actual reproductions of nature by herself, I 

 may, perhaps, be allowed to call some attention to them, not indeed 

 altogether through means of the book, but by exhibiting, with the 

 assistance of Prof. Tyndall and Mr. De la Rue, magnified optical 

 pictures of some glass copies from the original negatives. 



These will be better understood, if attention be turned for a 

 few moments to this large model of the Peak of Teneriffe, and a 

 tract of country about it, sixteen miles square. It has been pre- 

 pared for this special occasion by the enthusiastic kindness of my 

 friend Mr. James Nasmyth, C.E., long experienced in watching 

 lunar craters in telescopes of his own making ; and professionally 

 intimate with metals, fluid and solid, with all the volcanics, indeed 

 as well as the mechanics of the workshop. When he heard of a 

 terrestrial crater, the great crater of Teneriffe, eight miles in 

 diameter, he could not restrain his admiration and his zeal ; so setting 

 to work with all the map and measurement particulars which I 

 could furnish, he produced the present model, as accurate as the 

 existing state of our knowledge admits. 



By a general vertical illumination the colours may be most 

 distinctly seen. The green indicates vegetation, mainly confined 

 to the lower 4000 feet of altitude, or to the region below the 

 clouds. Above them are seen chiefly the colours of the lava rocks ; 

 the oldest, light yellow ; the most recent, black ; and the inter- 

 mediate, red. 



[The first collection of pictures shown illustrated, the scenery 

 of the green region on the northern coast ; the second had 

 its locale at a height of 8000 feet on Mount Guajara, or the 

 southern wall of the great elevation crater, submarine at the time 

 of its formation. And the third was confined to the eruption crater, 

 or central cone, constituting- the so-called Peak of Teneriffe ; and 



