Jupiter aphelion 



815 



Saturn 



1508 



Uranus ' ' 



3006 



Neptune ' ' 



4542 



Pluto 



? 



Chemistry and Physics. 211 



26.25 X (1.41)^«= 815 

 26.25 X (1.41)^2^1621 

 26.25 X (1.41)1* = 3222 

 26.25 X (1.41)1^ = 4543 

 26.25 X (1.41)1^ = 6407 



The perihelion distances have been quoted for the inferior 

 planets and the aphelion distances for the superior, on the 

 assumption that since the mass of Jupiter so far exceeds that of 

 any other planet it would influence the distances in ihese 

 directions. 



If it is surprising that this relation fits the planetary distances 

 so well, it is not less so that the author is able to apply a 

 similar formula to the satellites of Jupiter, Saturn, and Uranus 

 with nearly the same success. As he remarks, ''if this law had 

 been established in 1891 it would have been possible to have 

 predicted with a high degree of precision the position of the 

 5th, 7th, 8th, and 9th Satellites of Jupiter." Fulfillment of 

 prediction would have given great weight to a hypothetical law, 

 and it is a field that is still open for there are several vacant 

 places in Reynaud's tables. He has also developed curious 

 relations between the densities, the rotations and the inferior 

 limit of satellites but whether his formula is an approximate rep- 

 resentation of the progressive condensation of the solar nebula or 

 not, can hardly be answered until we have a better dynamical 

 theory of the evolution of a planetary system. f. e. b. 



9. The National Physical Lahoratory ; Report for the Year 

 1919. Pp. 151 with 37 figures. London 1920 (His Majesty's 

 Stationery Office). — A perusal of this report will leave the 

 impression that not all the consequences of the war are malign. 

 That critical period set on foot a great train of investigations 

 in the domain of physics, many of which promise a fruitful 

 harvest for the arts of peace. It is not possible to present any 

 resume of such a report, but opening it casually one may find 

 illustrations of the kind of thing just mentioned. 



P. 35. A catalytic lamp in which the combustion of gasoline 

 proceeds without the production of flame. The products of 

 combustion and the hot air may be utilized on aeromotor- or 

 other engines as such lamps may be inserted under the hood 

 without danger of fire. 



P. 60. The invention of a soft valve containing a silver 

 anode amalgamated with mercury. When used as a receiver for 

 loud wireless signals the illumination of the vapor due to colli- 

 sions makes it possible to read signals by visual observation 

 of the tube. 



P. 126. A successful study has been made of the alloys of 

 aluminum with copper and zinc, with iron and silicon, and 

 with magnesium and silicon. Tests have been made of their 

 fitness for general castings ; for working parts at high tempera- 

 tures, e. g. pistons of aero-engines ; for wrought material for 



