460 THE VOYAGE OF H.M.S. CHALLENGER. 



to the commencement of the .sand-flat. At the shores of the ereek the rocks are covered 

 with masses of excellent Oysters and Mussels, and other shell-bearing molluscs are 

 abundant, whilst a small Crab is to be found in numbers in every crevice. On the other 

 hand the water is overhung by numerous species of forest trees, by Orchids and Ferns, 

 and other vegetation of all kinds ; Mangroves grow only in the shallow bays. The Gum- 

 trees lean over the water in which swim the Trygon and Mullet, just as willows hang over 

 a pond full of Carp. The sandy bottom is full of branches and stems of trees, and is 

 covered in patches here and there by their leaves. Insects constantly fall on the water, 

 and are devoured by the Mullet. Land birds of all kinds fly to and fro across the creek, 

 and when wounded may easily be drowned in it. Wallabies swim across occasionally, 

 and may add their bones to the debris at the bottom. Hence here is being formed a 

 sandy deposit, in which may be found Cetacean, Marsupial, bird, fish, and insect remains, 

 together with land and sea shells, and fragments of a vast land flora ; yet how restricted 

 is the area occupied by this deposit, and how easily might surviving fragments of such 

 a record be missed by a future geological explorer ! The area occupied by the deposit 

 will be sinuous and ramified like that of an ancient river-bed. The inlet being so 

 extremely long and narrow, although the rise of the tide is two feet or more at the head of 

 the creek, the interchange of water with the ocean is very small ; the water in the upper 

 parts of the creek is merely forced back to a higher level by the tide below at flood-tide, 

 and similarly lowered again at ebb. Hence, after heavy rain, the surface water in all the 

 upper parts of the creek is so diluted by the torrent of fresh water from the stream, that 

 it becomes almost fresh ; indeed, at the time of the visit, it was for three or four miles 

 down, as far as explored, so slightly brackish as to be drinkable. At a little depth, 

 no doubt, the water was salt. Here are the most favourable conditions possible 

 for turning marine animals into fresh water animals ; in fact the change of mode of life 

 presents no difficulty. Below, no doubt the water is always salt, but the fish find a fluid 

 gradually less and less salt as they rise to the surface. Grey Mullet are caught here in 

 almost fresh water, and Oysters flourish in the same water, and with them Mussels and 

 Crabs ; abundance of Medusas were swimming in the creek above the sand -flats, where 

 there is scarcely any salt at all in the water, yet evidently in most perfect health. Occa- 

 sionally in times of long drought the water becomes as salt as the sea. A fisherman 

 said that after sudden very heavy freshes of water from the river, some of the shell-fish 

 sickened and died. He accounted for the presence of numerous dead cockle shells 

 (Cardium) in the bed of the creek, since he had never found the animals there alive, 

 by supposing that they had all been killed off by some unusual influx of fresh water 

 many years before. 



But beyond all that has been described, and beyond the extreme beauty of its wild 

 and rocky scenery, the Browera Creek has yet another interest ; it was in old times the 

 haunt of numerous aborigines, who lived on its banks in order to eat the Oysters, 



