A WONDERFUL HALO 
useful when you wish to keep up a certain speed in your 
marching. 
Eleven kilometres and a half from the last rapids, 
having travelled northwest, southwest, east, and even due 
south, so winding was the course of the river, we came to 
a tributary stream ten metres wide, on the left side of the 
Arinos. Eight kilometres farther we passed the inlet, 
then dry, of a small lagoon fed by the stream. The river 
banks, where eroded by the water, showed a lower layer 
of reddish-brown rock with a bright red ferruginous 
stratum above it. The top layer, ten feet thick, seemed 
formed of lime and alluvial deposits. 
We emerged into a large basin 200 metres across, with 
a charming little island in the centre forming two channels 
with fairly strong rapids. We followed the channel on 
the right. At that point the river folded over itself into a 
great elbow. A cliff, 120 feet high, towered on one side 
in brilliant red and yellow. The lower half of the strata 
were perfectly horizontal; the upper half at an angle of 
45° to the lower. The vivid colouring was intensified by 
contrast with a beautiful beach of immaculate white sand 
on the left side of the great elbow. 
I observed a wonderful double lunar halo on the night 
of July 7-8, the outer circle in successive tints of most 
delicate yellow, orange, pale blue and white, the yellow 
being nearest the centre. 
27 
