BY FRITZ NOETLING, M.A., Ph.D., ETC. 24 1 



(f) THE 40- FATHOM LINE. 



(PL. I., FIG. 6.) 



When the sea level has reached the 40-fathom lin^ 

 the western peninsula joins the mainland of Australia, 

 and within the broad isthmus now connecting Tasmania 

 and the mainland there appears a true inland lake, having 

 an area of 9,944, say 10,000 square miles ; that is to say, 

 about the size of Lak-e Erie. This lake has no outlet into 

 the open ocean, and it is distinctly divided into two por- 

 tions — a southern and a northern one. The southern 

 portion is the larger, and its greater axis runs almost 

 due north-south. The eastern and north-eastern shore 

 show numerous bays and fjords. The northern portion 

 is much smaller, and its larger axis runs north-west to 

 south-east. 



(g) THE 45-FATHOM LINE. 



(PL. L, FIG. 7.) 



We will now assume that if the sea level on both 

 sides of the isthmus recedes another 5 fathoms, the level 

 of the inland lake will do the same. Of course, this need 

 not be so ; it is quite possible that though the level of 

 the open ocean still receded that of the inland lake re- 

 mained stationary ; but for the sake of argument we will 

 assume that the level of the inland lake followed that of 

 the open ocean. 



The inland lake, as it would be shown by the 45- 

 fathom line, represents a basin whose main axis bears 

 north-west to south-east. A line from the mouth of the 

 Tamar to Port Phillip almost coincides with the direction 

 of this line. A large, narrow stretch of land which ex- 

 tends from the western shore, and which is nearly met 

 by another one from the eastern shore, subdivides the 

 basin into two parts, which communicate only by means 

 of a narrow and shallow strait. In fact, it is quite prob- 

 able that the two basins are separated. In this part of 

 Bass Strait the soundings are not very numerous, and 

 the course of the 45-fathom line is therefore somewhat 

 hypothetical. However that may be, whether connected 

 or separate, the southern basin is the larger, and it is 

 almost of circular shape, its main axis bearing almost due 

 north-south. The main axis of the smaller northern 



