April 23, I860.] SPOTTISWOODE ON TYPICAL MOUNTAIN RANGES. 97 



gravelly hollow, which was no doubt the dried up bed of the river. This was 

 the general character of the rivers, and it was quite possible that for several 

 years you might take a steamer up the Darling 1500 or 1800 miles, nearly to 

 its source, and that for the next ten years you would not be able to take a single 

 boat up. This resulted from the want of elevation in the mountain ranges. 

 The Murray Eiver, which was always navigable and a perpetually flowing 

 stream, took its rise from the Australian Alps, the summits of which were 

 covered for the greater part of the year with snow, the melting of which kept 

 up a constant supply of water. Still, even with this river it was only occa- 

 sionally that you got an opening into it from the sea. The mouth was blocked 

 up with sand, and there was not a greater depth than three feet over it, the 

 drainage of that part of the country not being sufficient to keep the mouth of 

 the river open, as it would do in a country where there was a regular fall of 

 water. He did not believe with Colonel Gawler that Lake Torrens was only 

 the ancient embouchure of the streams he had mentioned, but the present one, 

 and the only one it ever had, and that no more water had ever come out on an 

 average of years than came out now. These facts proved to him that there 

 could not be a well- watered country over the whole of the interior of Australia. 

 There might be large oases ; but generally it must be a diy country, or else the 

 overplus of drainage would come out in considerable rivers somewhere. The 

 fact mentioned by Gregory that after ascending the basin of the Victoria and 

 crossing the water-parting at no'greater height than 1400 feet, he soon came down 

 upon salt lakes, proved that it was an arid country, in which the evaporation 

 was greater than the waterfall, or the lakes would not have been salt. 



The springs mentioned by Sir Eichard Macdonnell were very curious and 

 interesting, and he was for some time puzzled by them. It appeared to him 

 that the water must contain a great quantity of carbonate of lime in solution, 

 and that these cups were nothing more than calcareous tufa that had been 

 deposited gradually by the overflow of the spring, until finally the deposit made 

 a mound, through which the water continued to well out, just as in the case of 

 the siliceous mounds round the geysers in Iceland. 



The third Paper read was — 

 3. On Typical Mountain Ranges. By William Spottiswoode, Esq., 



F.R.G.S. 



In an elaborate memoir published in the * Petersburg Transactions,' 

 Series VI. tom. viii., Dr. Abich has grouped the mountain ranges 

 of Western and Central Asia under four heads, and deduced a mean 

 direction for each group ; but in doing so he has simply taken the 

 arithmetical mean of the direction of the ranges under consideration, 

 without reference to their length or their elevation. Mr. Spottis- 

 woode shows the method by which the calculation of a mean direc- 

 tion ought justly to be made; not only by taking these omitted 

 data into account, but also by using the calculus of probabilities to 

 find whether or no, that mean direction be a typical one. Mr. Spot- 

 tiswoode's object is not so much to correct Dr. Abich's conclusions 

 on this particular point, which are, in fact, independent of the largest 



