When the night fell, dark and lowering, the lamp was lighted. They had never before seen an eight-wicked concentric burner in use. The shore lighthouses with which they were better acquainted were illuminated by electricity or on the catoptric principle, wherein a large number of small Argand lamps, with reflectors, are grouped together.
To interest them, to keep their eyes and ears away from the low-water orgy of the reef, he explained to them the capillary action of the oil. Although they had learnt these things in school they had not realized the exactness of the statement that oil does not burn, but must first be converted into gas by the application of heat. On the Gulf Rock there were nearly 3,000 gallons of colza oil stored in the tanks beneath, colza being used in preference to paraffin because it was safer, and there was no storage accommodation apart from the lighthouse.
Requiring much greater heat than mineral oil to produce inflammable gas, the colza had to be forced by heavy pressure in the cistern right up to the edge of the wicks, and made to flow evenly over the rims of the burner, else the fierce flame would eat the metal discs as well.
He read them a little lecture on the rival claims of gas and electricity, and demonstrated how dazzlingly brilliant the latter could be on a dark, clear night by showing them the fine light on the Lizard.
"But in hazy weather the oil wins," he said, with the proper pride of every man in his own engine. "Fishermen sailing into Penzance along a course equidistant from the two points tell me that if they can see anything at all on a foggy night they invariably catch a dull yellow radiance from the rock, whilst the Lizard is invisible. The oil has more penetrative power. Its chemical combination is nearer the mean of nature's resources."
At the proper time he banished them to the kitchen to prepare dinner, a feast diverted from the hour of noon by the chances of the day. He adopted every expedient to keep them busy, to tire them physically and mentally, to render them so exhausted that they would sleep in blissful calm through the ordeal to come.
As he could not leave the lamp, and they refused to eat apart from him, the dinner, in three courses, was a breathless affair. Going up and down five flights of stairs with soup, joint and pudding, whilst one carried the tray and the other swung a hand lantern in front, required time and exertion. They were cheerful as grigs over it.
Enid, whose turn it was to bring up the plates of tapioca, pleaded guilty to a slight sensation of nervousness.
"I could not help remembering," she said, "what an awful lot of dark iron steps there were beneath me. I felt as if something were creeping up quickly behind to grab me by the ankles."
"You should go up and down three times in the dark," was Brand's recipe. "When you quitted the door level for the third ascent you would cease to worry about impossible grabs."