194 



NATURE 



[April 14, 1910 



nearly three times as great— but the continuous in- 

 crease in emigration from Italy has placed it of recent 

 years at the head of the emigrating countries (Ireland 

 excluded). 



In all the countries considered, both birth- and death- 

 rates have fallen, and in the majority, especially those 

 countries (as Holland, Germany, and Austria) in 

 which the death-rate at the commencement of 

 the period was high, the fall in the death- 

 rate has exceeded the fall in the birth-rate, 

 as shown by the table below ; the natural 

 rate of increase was therefore greater at the end than 

 at the beginning of the period, in spite of the fall in 

 the birfh-rate. England is one of the exceptional 

 countries, for the death-rate, even at the commence- 

 ment of the period, was moderate, and the fall in the 

 birth-rate has rather more than kept pace with the 

 fall in mortality. 



Total 



. ... 23-8 32-5 137 



1 Figures in italics are partly estimated. 



6-6 



The factors contributing to the fall in the birth-rate, 

 which has recently attracted so much attention, are 

 analysed in detail by Sir Athelstane Baines. For the 

 most part it is clearly due to a fall in the fecundity 

 of married women of reproductive age. The propor- 

 tion of women of reproductive age to the population 

 has in many countries (as in the United Kingdom) 

 slightly increased, in other cases remained almost 

 steady or fallen very little. The proportion of such 

 women who are married, as shown by the table below, 



Country 



Number married per 1000 

 women aged 15-45^ 



Legitimate births per 1000 

 married women, 15-45! 



Total 



249 



490 500 276 



1 Figures in italics are partly estimated. 



has fallen in all the Scandinavian countries save 

 Denmark, but has increased m all the countries of the 



NO. 21 1 1, VOL. 83] 



central group, except England and Scotland. The 

 births per thousand married women of fertile ages, 

 on the other hand, have fallen in every country, with 

 the sole exception of Finland (and perhaps one should 

 add Norway), and most markedly in the central 

 European group. 



" The thirty years included in my survey," Sir Athel- 

 stane Baines concludes, " have been generally characterised 

 by a moderate rate of growth of population, interrupted 

 until towards the end of that period by considerable 

 emigration, since reduced, except in one or two cases. 

 People marry a little more than they did a generation ago, 

 and, in most of the countries reviewed, they marry earlier ; 

 but the growth in the relative number of the married has 

 been accompanied by a material decline in their output of 

 children. Illegitimate unions, also, whether less frequent 

 than before or not, at least contribute less to the tale of 

 births. The community is therefore almost everywhere 

 becoming an older one, with a gradually decreasing basis 

 for the coming generation. Thanks to a general improve- 

 ment in hygienic conditions, fewer succumb to disease, 

 especially in early life, and the mortality having decreased 

 more rapidly than the fertility of the population, the excess 

 of births over deaths is relatively not below, but, on the 

 whole, indeed, a little above that which prevailed at the 

 beginning of the period." 



?ROF. HANS LANDOLT. 



ON March 15, Geheimrat Prof. Landolt, the Nestor 

 of physical chemists, passed to his rest, full of 

 years and of honours. How few are left now of 

 that ardent band who, in the early 'fifties, came 

 under Bunsen's inspiration in romantic Heidelberg! 



In a brief notice it is impossible to give an adequate 

 picture either of the man or of his deeds. One is glad 

 to think, however, that his devotion to science will 

 be recognised in the memorial lectures by which the 

 various societies strive to do honour to the memory 

 of distinguished investigators. 



Hans Heinrich Landolt was born in Ziirich in 1831, 

 and began the study of chemistry in the university 

 of his native town. His Wanderjahre were spent in 

 Breslau, where he graduated, in Berlin, where he 

 studied under Rose and Mitscherlich, and, finally, in 

 Heidelberg. His progress in the academic career 

 was rapid. He became a Privatdozent in Breslau 

 (1856), an extraordinarius professor in Bonn (1858),! 

 and an ordinarius professor in Bonn (1867). He thenj 

 proceeded to the Technische Hochschule in Aachen. 

 In 1880 we find him in Berlin, where he occupied the 

 chair of chemistry in the Landwirtschaftliche Hoch- 

 schule until, in 189 1, he succeeded Rammelsberg as 

 director of the second chemical institute of the 

 university. When old age came upon him, his 

 enthusiasm did not wane ; he was active to the last. 



Landolt's researches were by no means confined to 

 one branch. In organic chemistry he studied, for 

 example, compounds of arsenic and antimony, the 

 action of potassium amide on various carbon com- 

 pounds, and the chemical changes in the flame ol 

 coal gas. In inorganic chemistry he dealt with sub- 

 jects such as phosphine, solid carbon dioxide, ammo- 

 nium amalgam, thiosulphurous acid in aqueous solu- 

 tion, the interaction of bromine and nitric oxide. Il 

 is, however, on his pioneering experiments on mole- 

 cular refraction and optical activity that his fame as 

 an investigator will last for all time. With th« 

 exception of the contributions of Biot, very little o" 

 importance had been done on the measurement O" 

 the specific rotations of optically active substance! 

 until the field was taken up by Landolt in a series 

 of papers which are models of exactitude. As a conse 

 quence of the experience he gained, workers in stereo 

 chemistry are indebted to him for numerous improve 

 ments in the technique of polarimetric observation. 



