G.—ENGINEERING. 119 
searching for cures for those troubles than the late Mr. James Weir. 
Beginning with his hydrokineter for circulating the water during the 
raising of steam, thus getting rid of strained boilers, he also tackled one 
of the chief causes of boiler corrosion, by his feed-heater and air and gas 
extraction. But this brought new trouble, for the fly-wheel pump could 
not pump the solid airless water ; this brought in his well-known straight- 
line pump. The careful filtering of the feed-water to eliminate oil and dirt 
and the use of evaporators for the supply of fresh water for ‘ make-up ’ 
were also notable advances. These and other improvements brougit 
freedom from many troubles in the use of high pressures. But these 
developments added many extra pieces of auxiliary machinery to the 
charge of the chief, and there are now separate centrifugals for condenser 
circulating water, perhaps separate air-pumps, and in turbines separate 
air-ejectors on the condenser. 
In condensers there are now several designs which lead to more com- 
pact and economical conditions. Still we have trouble with leaky tubes, 
an undesirable thing when water-tube boilers are used, especially small- 
tube boilers. The composition of the metal tubes was frequently blamed 
for these perforations, but a new theory is that it is due to a kind of water- 
hammer action arising from eddies and whirlpools generated in the circu- 
lating water forced to enter and leave small blunt-ended tubes. One 
remembers the researches made by Dr. Silberrad in 1908-13 on excessive 
damage to propellers in which he showed that this damage was mechanical 
in nature and properly termed erosion, and how his conclusions were sub- 
sequently confirmed by the investigations of Sir Charles Parsons in 1918-19, 
who proved that the mechanism of this erosion was due to a similar 
water-hammer action so severe as actually to cut away the metal. 
In no direction has advance been greater than in the use of electricity 
on board ship. My own experience was, I think, typical of that of other 
early workers in electricity. Swan and Edison invented the carbon- 
filament lamp about 1880, thus making domestic and ship lighting a pos- 
sibility. I remember while at Greenwich College seeing at the Crystal 
Palace, about 1881, an exhibition of Edison lamps, supplied with current 
by a dynamo with electro-magnets almost as tall as myself, and with a 
stray field so strong that it ruined all watches within yards of them. 
In 1884 the Arawa and Tainwi were fitted with incandescent 
electric lighting with stand-by oil lamps, as was, indeed, always done for 
some years thereafter, because of liability to failure of the electric plant. 
In 1884 the switches were made with wooden bodies, with no quick- 
break arrangements; sectional switchboards and fuseboards were un- 
known ; soldered joints on trunk wires insulated with rubber tape were 
made, and the wire available was little better than the modern bell-wire. 
But the interesting thing was that the two dynamos were alternating- 
current, ribbon-armature, 150-light Ferrantidynamos. This was fortunate, 
_ because, as the wiring was poor and the skin of the ship was used as the 
return, had the current been ‘ direct ’ there would have been great danger 
_ from electrolysis and consequent fires. The total power used was about 
380 horse. 
___ What developments there have been since then! Instead of the feeble 
20 kilowatts, hundreds of kilowatts are now in use on a vessel of the same 
size, and the current is used not only for lighting, but for ventilating, local 
heating, cooking, and for driving small machinery of all kinds, including 
