338 ANNUAL OF SCIENTIFIC DISCOVERY. 



than the colossal Peak of Teneriffe, of which, through the liberality of the 

 Admiralty, I am enabled now to lay some particulars before the Society. 

 First I would request attention to the fine model, on the scale of -g n -^^th, 

 kindly prepared for the occasion by my friend, Mr. James Nasmyth, who, 

 while employing upon it all that artistic skill for which he is so well known 

 to all present, has yet conformed most faithfully and conscientiously to all 

 the measurement, particulars of length, breadth, and height, that I could fur- 

 nish him with. The space thus represented is about sixteen miles square, 

 and embraces part of the northern coastline of the Island of TenerhTe, to- 

 gether with the Peak, the great crater, and all the most elevated parts of the 

 interior. The coloring is according to nature; the green near the sea-level 

 representing the vegetation, abundant at and below the summer-cloud level, 

 or four thousand feet ; above that line the hues of the lava rock predominate ; 

 the oldest, light and bright yellow, are the most extensive; the latest, black, 

 are chiefly confined to the upper part of the Peak, and to some special crater 

 mouths in the other parts; while the intermediate are red or brown. By 

 throwing a strong ray of side light on the model,* the variations of form 

 may be brought out prominently; and amongst them the huge size of the 

 " elevation crater " is most remarkable, being somewhat more than eight 

 miles in diameter. It is on the floor of this crater that has been formed the 

 central cone, known as the Peak of Teneriffe. From the brink of tl e south- 

 ern wall of the great crater, eight thousand nine hundred feet above the sea, 

 and two thousand feet above the crater-floor, and again, from a station on 

 the flanks of the central cone, at an elevation of ten thousand seven hundred 

 feet, excellent birds-eye views were obtained, during the two months we 

 spent there, over features of the volcanic landscape; which then, seen in 

 the thin transparent air above the clouds, and under a vehement solar illu- 

 mination, assumed very much indeed of a lunar look. In comparing these 

 features with lunar volcanoes, the first remark may be, that our great crater, 

 eight miles in diameter, is still nothing to compare with man} 1 - in the moon, 

 some fifty or sixty miles in diameter, Are those great lunar circles, then, 

 therefore, not craters ? To this end we may answer : 1st. That the fre- 

 quency with which small craters break through the walls of large ones in 

 the moon, and never large through small, indicates that the earlier volca- 

 noes there were, on the whole, always the larger; and this practical result 

 is quite agreeable to the theory of volcanic action, which ascribes its lead- 

 ing features to the remains of heat due to the mode of planetary formation. 

 2d. That, so far as Teneriffe is concerned, the large volcano was the earlier, 

 as, too, it should be, according to the theory just mentioned, which is equally 

 applicable to the earth as to the moon. The distance, however, which we 

 can go back in the volcanic history of the earth, is as nothing compared to 

 its actual age, or compared to what we can in the moon, for this very simple 

 and patent fact, the presence of an ocean on the earth, combined with sec- 

 ular variations of land and sea surface. These variations, which are still 

 going on, have been in force for such immense periods of time, that geolo- 



* This was done at the lecture by means of a Drummond lime-ball light, which 

 was afterwards employed in magnifying arid exhibiting, by optical pictures, a series 

 of thirty-six photographs of volcanic features, at from 7,000 to 12,200 feet above 

 the sea-level. Mr. Nasmyth had also very kindly allowed six of his large and un- 

 equalled drawings of the moon's surface to be suspended in the room, for the pur- 

 pose of contrast and comparison. 



