548 



NATURE 



[October 13, 1923 



1922, pp. 387-389. From the rejjcated trials made, it 

 was definitely proved that the gases so collected are 

 free from water. Thus the theory of the anhydrous 

 nature of the magmatic gases, advanced by AU)crt 

 Brun, receives fresh experimental confirmation. 



on the cyclonic movements caused by convection 

 currents in the hot air over the lava-flow. 



In honour of the King and the Premier, the 

 demia Gioenia di (^tania has given the name \iu.m, 

 Emanuele III. to the new craters in the upper j)art u\ 



Fig. 3. — Explosion-craters, Vittorio Emanuele III. 



\rhoto: (,'. PoHtt. 



Many observations were made of the temperature 

 of the lava, and it was found that this varied in different 

 parts of the flow owing to superficial cooling in contact 

 with the air. At a temperature of from 670° to 690° 

 the lava was still pliable, and could be easily bent and 

 compressed. Some interesting observations were made 



the eruptive region, and has named those near the vent 

 from which the lava issued Crateri Mussolini. 



Many foreign vulcanologistsTamc to see the eruption, 

 and among them I had the pleasure of seeing Dr. G. 

 Kemmerling, chief of the Vulcanological Ser\-ice of 

 the Dutch Indies. 



Population and Unemployment.^ 



By Sir William li. Beveridge, K.C.B. 



THE impression that the civilised world is already 

 threatened with over-population is ver}' common 

 to-day. Many, perhaps most, educated people are 

 troubled by fear that the limits of population, 

 probably in Europe and certainly in Great Britain, 

 have been reached, and that a reduction in the rate of 

 increase is an urgent necessity. Most, if they were 

 asked to give reasons for their fear, would refer to one 

 or both of two reasons : they would point to the 

 enormous volume of unemployment in Britain ; they 

 would say that economic science, at least at Cambridge, 

 had already pronounced its verdict. I propose to 

 begin by raising some doubts as to the validity of each 

 of these arguments. 



The volume of unemplo\Tnent in Britain is un- 

 doubtedly serious, and almost certainly unparalleled 



' From the presidential address delivered to Section F (Economic Science 

 and Statistics) of the British Association at Liverpool on September 17. 



NO. 2815, VOL. I 12] 



in past history. Those who see, as we now do, more 

 than a million wage-earners whom our industrv' for 

 years together is unable to absorb in productive 

 employment may be excused if they draw the inference 

 that there are too many wage-earners in the countr\'. 

 The inference, though natural, is unjustified. Un- 

 employment in Britain can in any case prove nothing 

 about the world as a whole. History shows that it 

 does not prove over-population even in Britain. 



During the last half of the nineteenth century, the 

 industry of the United Kingdom was finding room for 

 a rapidly increasing number of wage-earners with an 

 admittedly rising standard of production and comfort. 

 Through the whole of that period there was unemploy- 

 ment in the country. The percentage of trade unionists 

 out of work never fell to zero ; in no year since 1874 

 was it less than two ; at more than one crisis it reached 

 a height comparable if not equal to that which we have 



