TRANSACTIONS OF SECTION G. 787 



Teplaced by catoptric oil light apparatus at Saint Bees Lighthouse on the coast of 

 ■Cumberland. With Winstanley's structure on the Eddystone in 1696 may be said 

 to have commenced the modern engineeiing efforts *in directhig the great sources 

 of power in nature for the vise and convenience of man ; ' ' efforts which, followed 

 up by Rudyerd, Smeatou, the Stevensons, and others, have since been so successful 

 in converting hidden dangers into sources of safety, and ensuring the beneficent 

 guidance of the mariner in his trackless path. These works of modern mechanical 

 science are now to be found around all the nautical centres of civilisation and com- 

 merce, and are so numerous that time will not permit of my referring, except 

 incidentally, to any of them at home or abroad. I will therefore proceed to the 

 particular branch of mechanical science to which I desire to invite your attention, 

 viz. lighthouses, light-vessels, buoys, and beacons. 



During the last century a very considerable increase has occurred in the number 

 of lighthouses and light-vessels on the various coasts of the world, which have 

 been required to meet the rapid growth of commerce. Only during the last 

 twenty-five years can accurate statistical information be obtained, and it is found 

 that in the year 1860 the total number of coast lights throughout the world did 

 not exceed 1,800, whereas the present number is more than 4,000. 



The relative progress of each of the chief maritime countries, in the extension 

 of their system of lighthouses and light-vessels between 1860 and 1885, is shown 

 approximately in the statement on the nest page, from which it will be observed that 

 Japan, which had not a single coast light in 1860, has now fifty-seven, eight of these 

 being lights of the first class ; while China, which had only four secondary coast 

 lights in 1860, has now fifty-five lights, fourteen of these being of the first class. 

 The greatest increase, however, is found in British America, where in 1860 there 

 were only ninety-one coast-lights, whereas in 1885 there were 636. 



Concurrently with the enormous increase in the number of coast lights during 

 the last fifty years, very great improvements have been effected from time to time 

 in their efficiency. In 1759 Smeaton's lighthouse on the Eddystone was illumi- 

 nated by 24 tallow candles, weighing | lb. each. The intensity of the light of 

 each candle, I find, from experiments made with similar candles prepared for the 

 purpose, to have been about 2-8 candle units each ; thus the aggregate intensity of 

 radiant light from the 24 candles was only about 67 candle units. No optical 

 apparatus, moreover, was used for condensing the radiant light of the candles, and 

 directing it to the surface of the sea. The consumption of tallow was about 3-4 

 lbs. per hour ; therefore, the cost of the light per hour, at the current price of 

 tallow candles, would be about Is. 6ff/., sufficient to provide a mineral oil light, at 

 the focus of a modern optical apparatus, to produce tor the service of the mariner 

 a beam of about 2,400 times the above-mentioned intensity- 



Tlie uitroduction of catoptric apparatus for lighthouse illumination appears to 

 have been first made at Liverpool, about 1763, and was the suggestion of William 

 Hutchinson, a master mariner of that port. The invention by Argand, in 1782, of 

 the cylindrical wick lamp, provided a more efficient focal Uiminary than the flat 

 wick lamp previously employed, and was soon generally adopted, for both fixed and 

 revolving lights. In 1825 the French lighthouse authorities effected another very 

 important improvement in lighthouse illumination by the introduction of the diop- 

 tric system of Fresnel in conjunction with the improvements of Arago and Fresnel 

 on the Argand lamp, by the addition of a second, third, and fourth concentric 

 wick. 



Coal and wood fires, followed by tallow candles and oil, have been referred to 

 as the early lighthouse illuminants. In 1827 coal gas was introduced at the Troon 

 Lighthouse, Ayrshire, and in 1847 at the Hartlepool Lighthouse, Durham, the 

 latter for the first time in combination with a first-order Fresnel apparatus. The 

 slow progress made with coal gas in lighthouses, except for small harbour lights, 

 where the gas could be obtained in their vicinity, was chiefly due to the great cost 

 incurred in the manufacture of so small a qu'antity as that required and at an iso- 

 lated station. In 1839 experiments were made at the Orford Low Lighthouse, 



' Charter of the Institution of Civil Engineers. 



3 E 2 



