Chap. VI. ELECTRIC PHENOMENA. 281 
sweet water, the so-named " Lower Springs," near which 
we halted. 
In the evening the lightning played all around, and heavy 
clouds promised rain ; but only a few drops fell. As I 
was standing on guard, between nine and eleven o'clock, I 
saw a waving light over the heights on the north side of 
the valley : its motion resembled that of the fluctuating 
reflections of the Fata Morgana, under a gentle agitation 
of the air. Two bright points suddenly appeared, like 
rising stars, but soon vanished again. This light I ob- 
served for above half an hour. During the whole time 
the sky was clouded, and there is no doubt that this luminous 
phenomenon was seated within the stratum of air imme- 
diately above the ground. 
On the north side of the river the road runs along 
it — one while through the valley, at another ascending 
to the plateau over banks of sand and conglomerate. Small 
semi-spherical cacti grew at the top upon the hard clay soil, 
while here and there small patches of grass, of different 
species, covered the ground. In the distance we saw hills 
of drift-sand, the forms of which recalled those of the snow 
on Alpine summits heaped up by the wind. When at the 
bottom we again came upon the river : nothing was to be 
seen of it but a few saltwater-pools between drift-sand and 
scattered reeds. In some places there was hardly any 
river's bed perceptible : the drift-sand had filled it up, and 
salt-grass or reeds had overgrown it. It looked as if no 
water had flowed here for years, and this may perhaps 
have been the case. The sand was covered with salts, 
which, to judge from the taste, consisted of a mixture of 
common salt and sulphate of magnesia. 
On the 17th of September we n eared the " Middle 
Springs " at nightfall, as a storm was approaching, and at 
