cxii. PRESIDENTS ADDRESS. 



has been known for several years, and is now practically carried 

 out, those containing no pearls being returned to the water. 

 Though instantaneous photographs have not yet been taken with 

 these rays, the time of exposure has been greatly reduced, and it 

 is hoped that before long the action of the heart and other 

 organs may be shown by the cinematograph. The single plates 

 from which a photograph can be taken in its natural colours, by 

 one process, form the most prominent feature of the year's 

 photographic advances. The plate is viewed as a coloured 

 transparency, and cannot be used to print from in colours. The 

 successful manufacture of crucibles and other vessels out of 

 iridium, rhodium, and fused silica is a great boon to chemists 

 in dealing with refractory substances which melt at very high 

 temperatures. The two metals have hitherto been unworkable 

 through impurities, but are now produced in such a pure state as 

 to be malleable. Their melting point is very high, and they are 

 unaffected by acids. Silica also melts only at a very high 

 temperature, and is fashioned when viscid into the forms 

 required. My last note under Chemistry seems to upset our 

 ideas of the spectra of substances, inasmuch as it has been 

 shown that caesium, rubidium, and potassium have two inde- 

 pendent spectra totally different from each other, the new spectra 

 being produced by powerful condenser discharges, instead of 

 the electric arc. In this direction we can only await further 

 developments. 



ENGINEERING. 



Though the aeroplane cannot yet be said to be anything more 

 than a dangerous toy, it has yet been successful in covering a 

 kilometre, including a complete turn at half the distance, in a 

 French public competition. Also at Issy les Moulineaux on 

 March nth last, an aeroplane traversed 10 kilometres in 9^ 

 minutes round a marked circuit. In private it has doubtless 

 done somewhat more. Airships propelled by motors are more 

 satisfactory, but not very reliable. A sensational achievement of 



