The Earth in Opposition. 377 



or Mercury ; and though, of course, demonstrative certainty in 

 the reply is not within our reach, we may be led to some inte- 

 resting conclusions. We shall of course suppose the case of 

 the nearest approach of either of those planets when they pass 

 between ourselves and the sun. In such circumstances, as was 

 explained in No. VIII. of the present work, an apparently 

 retrograde motion will bring us up with a great broad disc into 

 their midnight sky, and all our features will lie open before the 

 distant observer's gaze. There can be little question that the 

 distinction of our continents and oceans would be very per- 

 ceptible, from the superior reflective power of the former as 

 contrasted with the absorbent property of the latter, which, as 

 is shown by experiments with the diving bell, soon extinguishes 

 the solar rays. The general aspect of the land would no doubt 

 be various from the effect of local colour where sufficiently 

 extensive, and the vegetation of the prairies and pampas would 

 be readily distinguishable from the sands of the Sahara; but 

 diversities on a smaller scale would be merged by distance in a 

 compotind gray of the third order of colour : the appearance of 

 the water would also be greatly contrasted in different parts, 

 from its varying degrees of depth and consequent translucency. 

 Islands would, of course, be in general perceptible in proportion 

 to their size as brighter specks ; but it may admit of a question 

 whether an island, or, indeed, a line of coast, would be in all 

 cases easily distinguished from an adjacent shallow sea.* The 

 polar regions of ice and snow would of course be strongly 

 marked, with their extension or contraction according to the 

 time of year; but in consequence of the inclination of the 

 earth's axis, then presentation would differ greatly at different 

 seasons : if the supposed opposition of the earth should coincide 

 with our European summer, the N. snows would alone be conspi- 

 cuous, entering far into the visible hemisphere, but diminishing 

 gradually with the continued action of the sun ; if during our 

 winter, the reverse would occur; in spring or autumn each 

 pole would show its white segment at the edge of the disc ; 

 but in every case, as our poles of temperature are not coincident 

 with our poles of rotation, and our continental are very different 



* " At the eastern extremity of the island, where the rocks break off steeply 

 some hundreds of feet, we saw every object of the port nearly beneath, and 

 apparently within stone's throw. A novel sight to ns was the bottom of the 

 harbour, seen through the clear greenish water with considerable distinctness 

 almost from end to end. Patches of sea-weed, dark rocks, and white gravel, 

 seemed to be lying in the bottom of a shallow mirror, across which small fishes, 

 large ones in reality, were wandering at their leisure. This was a picturesque 

 revelation. Upon the surface of the harbour the depth of water very nearly 

 shuts out all view of the bottom. I am beginning to think, that a few thousand 

 feet above the ocean, hi a bright day, would enable the eye to pierce it to an 

 extraordinary depth.' ' — Noble's After Icebergs with a Painter, pp. 182, 183. 

 VOL. II. NO. V. D D 



