PRESIDENTIAL ADDRESS. 27 



driven alternators with a rated capacity of 21,500 kw., but 

 which can generate during an emergency about 30,000 kw. 



At both stations the equipment of boilers and their 

 appurtenances, switch gear, indicators, meters, and other 

 electrical appliances are of the most modern type ensuring 

 safety and economy in working. 



The current generated at these two stations is converted 

 into direct current by rotatory convertors at sixteen sub- 

 stations, and from them distributed to the overhead trolly 

 wires. When the system was first introduced large storage 

 batteries were provided, but the necessity for these has 

 disappeared, for it has been found cheaper to lay duplicate 

 mains and provide more convertors to obviate the risk of 

 interference with traffic in consequence of a breakdown 

 of a machine or cable. 



The current for operating the lines on the northern side 

 of the harbour, is conveyed by cables laid in a tunnel under 

 the harbour, starting at Long Nose Point. The construction 

 of this involved some engineering difficulties, for although 

 it is 135 feet below the bottom of the harbour at that point, 

 silt and sand broke in through an unsuspected fissure, filling 

 the tunnel. It was subsequently cleaned out and the 

 fissure closed up. 



In 1902 the "Thermit" welding of the tram-rails was 

 introduced; prior to that time, in order to obtain the proper 

 electrical and mechanical connection between the rails, 

 extra long fish plates, carefully planed and fitted to the 

 rail were used; this, after being in use for fourteen years, 

 has now been dispensed with in favour of electric welding, 

 which is both cheaper and more efficient. Instead of the 

 rails being welded at the ends they are carefully butted 

 end to end, and then fish plates are welded to the sides of 

 the rails, forming a mechanically good joint and an efficient 

 conductor for the return current. 



