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



245 



less, and that from 15 to 20 fathoms considerably higher, 

 than the average. It is, however, impossible to give 

 even fairly accurate estimates, because the rate of in- 

 crease apparently does not follow a regular law. We see 

 that between 25 and 40 fathoms it increases, and from 40 

 to 50 fathoms it decreases again. 



For the same reason it is impossible to give the cor- 

 rect ratio in per cents. We may say 6,916 square miles, 

 representing in the aggregate 63.172 per cent, of the land 

 shown in the map, have been added to it; but if I were 

 to add only a short strip of land both to Australia and 

 Tasmania, this would in no way alter the addition to the 

 coast line, but it would at once alter the percentage. 



The same argument applies to the increase between 

 the 20 and 25 fathom line. We know the absolute in- 

 crease in square miles, but nothing of the area of the 

 20-fathom line is known, except that it must be larger 

 than 10,855, t>ut smaller than 17,771 square miles ; a per- 

 cental figure cannot be calculated. 



The average increase of land between o and 50 

 fathoms is 5,293 square miles for every 5 fathoms of 

 depth, but it is clearly shown during the different stages 

 that the ratio of increase varies considerably. The 

 greatest increase takes place between the 35 and 40 

 fathom line, and thence it decreases in both directions. 

 This plainly indicates one fact ; the agencies responsible 

 for the change of land into water have been increasing 

 in force, first slowly, then quicker, till the maximum was 

 reached between the 35 and 40 fathom line, and then 

 their energy commences to decrease again. We will see 

 later on that this fact deduced from the increase or de- 

 crease of area as the case may be is fully corroborated 

 by certain geological changes known to us. 



