78 Notices respecting New Books. 
Mont Blanc. He also made an investigation into the connexion 
between sun-spot frequency and mean aunual temperature, em- 
ploying records from a considerable number of tropical stations, 
extending over at least one sun-spot period. Only mean results 
from all the stations combined are given, so that the reader 
cannot judge fully the part played by chance. The author appears 
to confirm the result reached by Koppen in 1873, that in the 
Tropics mean temperature diminishes as sun-spots increase. 
Between years of absolute maximum and minimum of sun-spots 
Nordmann (p. 18) finds an average difference otf 0°26 C. Even 
supposing this small difference to be true for the whole surface 
of the earth, it would not necessarily follow, as the author seems 
to conclude, that the sun’s thermal radiation diminishes as sun- 
spots increase. It may also be noted in passing that it is open 
to doubt whether attention should not rather be given in this 
connexion to the mean diurnal range of temperature. 
The future alone can show the real value of the theoretical part 
of the Thesis. The author displays a nimble mind, and his 
reading seems catholic and remarkably up to date. An English 
reference is as recent as March 1903, and one would infer a close 
study of the recent papers of Huggins, Ramsay, and others, 
especially of J. J. Thomson and his school. The free use of very 
recent results has its risks, even when guided by critical insight ; 
and an intimate knowledge of all the subjects to which Nordmann 
applies his theories is perhaps rather too much to expect of any 
one man. As exemplifying the dangers to which too rapid 
speculation leads, reference may be made to p. 64. Values are 
there quoted for diurnal ranges of declination at Batavia in 1895. 
The figures given actually appear in the Batavia ‘ Observations ’ 
(Table 26), but they have a totally different meaning from what 
the author supposes. The true ranges (obtainable from Table 18, 
1. c.) are much smaller, being less than the values the author quotes 
for Nice. ‘he mistake may mean undue haste in a single instance, 
but no expert in Terrestrial Magnetism is likely to retain un- 
diminished confidence in a writer who follows this up by laying it 
down as a general law (“loi générale ’’) that the amplitude of the 
diurnal variation of magnetic declination diminishes as one retires 
from the equator! The eminent triumvirate to which the Thesis 
was submitted must surely have overlooked this statement. If 
the mathematical work on p. 115—in connexion with an estimate 
of auroral frequency—satisfied Prof. Poincaré, it presumably is 
correct, but the reviewer must confess to an inability to reconcile 
it with the physical problem proposed. The author is unusually 
successful in his spelling of English names, but he follows an 
American and erroneous authority when he talks—as he does 
repeatedly—of the “ Addie” magnetograph; and when he locates 
this instrument at Greenwich, and describes Prof. Turner as 
“chef du service magnétique,” he adds a little to the confusion. 
As the author is described as ‘“‘ Astronome a l’Observatoire de 
Nice,” he is presumably more thoroughly at home with the astro- 
nomical subjects treated, and his discussions of the Corona, Nebule, 
and Nova Persei if slight are certainly suggestive. 
