cealed by a scanty growth of spinifex, the reflection from its surface caused the passing clouds to be coloured a deep purple. We had long passed the limit to which the tropical rains of the north-west coast extend, and the country south of 19° seemed only to be visited by occasional thunderstorms. Thus for a few miles the grass would be fresh and green, then there would be a long interval of dry, parched country, where no rain appeared to have fallen for a twelve-month. The channel of the creek also decreased in size, and the frequent occurrence of salicornia indicated the saline nature of the soil; the water became brackish, then salt, and finally spread out and terminated in the dry bed of a salt lake, a mile in diameter, which communicated with a second, of larger size, nine miles long and five wide. Though now quite dry, there were marks of water having stood for considerable periods, of from 10 to 15 feet deep, as the shells of mussels in their natural position were abundant more than a mile from the ordinary bank of the lake, showing that a large tract of country is sometimes inundated. As the mussels are a species which live in fresh water, it is evident that at such times the lake is not salt, but it would appear that as the waters evaporate and recede they become saline, as the shells found within the limits of the lake were of other species which affect brackish or salt water." One more attempt to make for the south proved abortive, and, with many regrets, Gregory returned to the depôt, after having penetrated within 730
