PRESIDENT'S ADDRESS. Ixxv. 



by ordinary chemical forces. He points out that we are 

 far from being able to reproduce such products by means 

 similar to the vital ones, and until we have some definite 

 knowledge of how the vital processes are carried on and can 

 imitate them in our laboratories we have not much ground 

 to go upon. The National Physical Laboratory is now in 

 possession of a British Radium Standard, and is prepared to 

 standardise preparations of radium and mesothorium. The 

 chief source of radium is the mineral carnotite, from Colorado, 

 and, the process of extraction having been improved, more 

 can be obtained per ton of ore. It has been found that the 

 percentage of radium in accessible rocks is much more than 

 enough to sustain the earth at its present temperature, were it 

 to be as abundant through its whole mass. In order, there- 

 fore, that the earth may be kept at its present heat it seems 

 necessary to assume that the bulk of the radium it contains 

 is concentrated near its surface. Remarkable results have 

 taken place by passing X-rays through zinc -blende and other 

 crystals, the issuing rays, when received on a photographic 

 plate, recording a geometrical pattern of spots, which, by 

 placing photographic plates at different distances, are shewn 

 to be formed by rectilinear pencils of rays spreading in all 

 directions from the crystal. These appear to be the reflections 

 of the X-rays from the similar and similarly situated planes 

 of atoms composing the crystal, in other words the planes of 

 the space lattice. It is considered as more likely that the 

 reflections come from the sides of one set of atoms composing 

 the molecules of the crystalline substance than from the sides 

 of the actual molecules, and that much may be learnt from these 

 experiments of the atomic structure, and perhaps even of the 

 size and other details of the atoms themselves, and that it 

 forms a new departure in our knowledge in this respect. 



ENGINEERING. 



The development of aeroplanes is still continuing, and is 

 perhaps most strikingly seen in the wonderful feats accom- 

 plished by certain aviators which are so much before the 



