PRESIDENT'S ADDRESS. 15 



six isotopes, or forms differing very slightly in atomic weight 

 and some other respects, but all sufficiently like each other to be 

 classed as lead. They are obtained in different ways, and it 

 has now been discovered that the spectra of two of them differ 

 slightly, namely ordinary lead and lead derived from pitch- 

 blende residues. 



ENGINEERING. 



The improvements which were made in aeroplanes during 

 the war still continue, and many long flights have been made 

 which shew the endurance and powers of these machines and 

 their pilots. The first was the flight across the Atlantic 

 which, as regards the direct flight from Newfoundland 

 to Ireland, was first made in June last in 16^ hours, giving 

 an average speed of about 120 miles an hour. Since 

 then, amongst other long distances, flights have been made 

 by stages from England to Australia, and Cairo to the Cape. 

 The record height of 36,020 feet (nearly 7 miles) has also 

 been reached. The direct trans-Atlantic trip has also been 

 made by airship, the average rate being 33 miles per hour 

 over the course of 3,100 miles, or little more than a quarter of 

 the speed of the aeroplane. The airship also made the 

 return journey, the speed being greater owing to the wind 

 being more favourable. The commercial use of airships 

 and aeroplanes has been much under consideration; but little 

 has been practically carried out in this direction. The 

 address of the President of the Engineering Section at the 

 British Association was on the subject of Engineering and 

 science during the war, arrd gave a very interesting account of 

 the production and use of guns and ammunition and of 

 tanks and aircraft, as well as of submarines and mines, and 

 the means adopted for protection against them and for their 

 destruction. A good deal was also said on this subject by 

 the President of the Association in his Inaugural Address. 

 The flame projectors invented and first used by the Germans 

 with such horrible effects, have since the war been found 



