544 



NA rURE 



[September 26, 1907 



\\'ith regard to the restoration in the flesh, the photo- 

 graph which I send you was made by my friend Mr. 

 C. H. Angas, a skilful delineator of animals, with such 

 help as we could give him from the anatomist's point of 

 view. There can, I think, be little doubt that in its 

 general build the Diprotodon had considerable resemblance 

 to a gigantic wombat, and as such we have drawn him. 

 Opinions may, however, differ as to our treatment of the 

 muzzle. The huge overarching nasals, which greatly 

 exaggerate the somewhat similar formation in the tapir, 

 and the very massive bony internarial septum, must in- 

 dicate some special, and probably some protuberant, 

 development of the soft parts in this region. Bearing in 

 mind the many cranial, as well as other skeletal, re- 

 semblances between Diprotodon and Macropus, we have 

 consequently assigned to the former in our restoration 

 a snout of the same type as that of the latter animal, but 

 of greatly exaggerated size and prominence. In the case 

 of the ears, we have compromised between the extremes 

 of length of those organs as they occur in the kangaroos 

 and wombats, with, however, a nearer approach to the 



I might add, though the information has already 

 appeared in your columns, that a copy of this cast is in 

 the possession of the Zoological Museum at Cambridge 

 University, and that portions of it, together with some 

 original bones, have been sent to the Natural History 

 Department of the British Museum. Replicas of it have 

 also been sent to the museums of Melbourne, Victoria, 

 and of Perth, Western ."Xustralia. 



E. C. Stirling. 



The Museum, .Adelaide, South Australia, August 6. 



The Origin of Radium. 



In a communication published in Nature of November 

 IS, 1906, I described some e.xperiments which had given 

 results indicating the growth of radium in a preparation 

 of thorium which had been previously precipitated in a 

 solution of a uranium mineral. I had found from other 

 e.xperiments that the thorium after this treatment con- 

 tained a radio-active body which did not decay appreci- 



former proportions. The result, on the whole, has been 

 to make the head appear much more like that of a very 

 massive and bulky kangaroo than of a wombat. In the 

 original sketch we have presumed the animal to be covered 

 with a very dark short fur of wombat type. For a setting 

 we have delineated the Diprotodon amidst surroundings 

 that represent some present characteristics of Central 

 Australia. Thus in the background, to the left, is part of 

 the white expanse of one of those large salt-encrusted 

 clay pans of which Lake Callabonna, where the bones 

 were found, is an example. In the distance beyond the 

 lake is shown one of the flat-topped hills that are very 

 characteristic of the " desert sandstone " region of the 

 interior. The vegetation in the foreground is chieflv 

 " salibush " (Atriplex spp.), some species of which, 

 together with allied plants, having apparently formed the 

 principal food of the Diprotodon, just as these now supplv 

 the chief sustenance of the introduced Herbivora, while 

 here and there is a trailing plant of " parakylia " 

 (Llaytonia spp.). so well known to travellers in the dry 

 central regions for its moisture-holding properties. 

 NO T978, VOL. 76] 



ably in the course of several years. It was a simple 

 matter to demonstrate that this active substance was not 

 radium, uranium, or polonium, and I therefore assumed 

 that it was actinium, since Debierne has stated {C.R., 

 cxxx., 906) that ihe chemical properties of actinium 

 are similar to those of thorium, and since, moreover, an 

 emanation which completely lost its activity in less than 

 half a minute was evolved in small amounts from the 

 oxides of the thorium treated in this manner. I there' 

 fore suggested that actinium was the parent of radium 

 and the intermediate product between uranium and 

 radium. 



Rutherford has recently given an account (Nature, 

 June 6) of some experiments in the course of which a 

 solution of actinium was successively precipitated with 

 ammonium sulphide in order to remove the radium 

 present. From the results obtained he concludes that the 

 parent of radium is distinct from actinium, and is 

 separated from the latter by precipitation with ammoniuir. 

 sulphide. 



For the past ten months I have been continuing my 



