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Sept. 23, 1886 | 
NATURE 
503 
sumption 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 ts. 6$¢., sufficient to provide a mineral oil light, 
at the focus of a modern optical apparatus, to produce for the 
service of the mariner a beam of about 2400 times the above- 
mentioned intensity. 
The introduction of catoptric apparatus for lighthouse illu- 
mination 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 lumin- 
ary 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 dioptric system of Fresnel in conjunction with the improve- 
ments of Arago and Fresnel on the Argand lamp, by the addi- 
tion 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, 1 urham, 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 manu- 
facture of so small a quantity as that required and at an isolated 
station. In 1839 experiments were made at the Orford Low 
Lighthouse, Suffolk, with the Bude light of the late Mr. Golds- 
worthy Gurney. This light was produced by throwing oxygen 
gas into the middle of a flame derived from the combustion of 
fatty oils. The flame was of the dimensions of that of the 
Fresnel four-wick concentric burner. An increased intensity over 
that of the flame of the large oil burner was obtained, but it was 
not found to be sufficient to justify the increased cost incurred. 
In 1857 a trial was made by ihe Trinity House, at Blackwall, 
under the advice of Faraday, with one of Holmes’s direct cur- 
rent magneto-electric machines for producing the electric are 
light for a lighthouse luminary, and the experiment was found to 
be so full of promise for the future that a practical trial was 
made during the following year. 
At the South Foreland High Lighthouse, on December 8, 
1858, the first important application cf the electric arc light, as 
a rival to oil and gas for coast lighting, was made with a pair of 
Hclmes’s machines, and thus were steel magnets made to serve 
not only, as in the mariner’s compass, to guide him on his path, 
but also to warn him of danger. In 1859 the experimental trials 
at the South Foreland were discontinued, but they were <uffi- 
ciently encouraging to lead to the permanent installation of the 
electric light at Dungeness Lighthouse in 1862. In 1863 the 
electric arc light was adopted by the French lighthouse authorities 
at Cape La Héve. 
In 1871, after practical trials with a new alterrating current 
machine of Holmes, two of such machines were supplied to a 
new lighthouse on Souter Point, coast of Durham, and in the 
following year the electric arc light, with these machines, was 
established in both the High and Low Lighthouses at the South 
Foreland, where it «till shines successfully. The early experience 
with the electric light at Dungeness was far from encouraging. 
Frequent extinctions of the light occurred from various causes 
connected with the machinery and apparatus, and the oil light 
had, at such times, to be substituted. As no advantage can 
counterbalance the waut of certainty in signals for the guidance 
of the mariner, no further step in the development of the electric 
light was taken by the Trinity House until the latter part of 
1866, when favourable reports were received from the French 
lighthouse authorities of the workingof the Alliance Company's 
system at the two lighthouses of Cape La Héve. Complaints 
were also received from mariners, in the locality of Dungeness, 
of the dazzling effect on the eyes when navigating, as they arethere 
_ frequently required to do, close inshore, thus being prevented from 
rightly judging their distance from this low and dangerous point. 
Therefore, in 1874, the electric light was removed from Dunge- 
ness, and a powerful oil light substituted. In 1877 the electric 
arc light was installed at the Lizard Lighthouses on the south 
coast of Cornwall, and arrangements are now being made for 
establishing it at St. Catherine's Lighthouse, Isle of Wight, and 
at the High Tower, on the Isle of May, Firth of Forth. I have 
mentioned that the first machines of Holmes at the South Fore- 
land were direct current, the machines provided by him for 
Dungeness ‘being also of the same type. The French lighthouse 
authorities, however, adopted for their lighthouses at Cape La 
Héve the ‘Alliance’ alternating current magneto-electric 
machines, and, in consequence of the less wear and tear of these 
machines with greater reliability through their having no com- 
mutator, Holmes was required to supply alternating current 
machines for Souter Point and the South Foreland. Those 
machines have been running at these stations fourteen years and 
fifteen years respectively. They have during this period required 
only a very trifling amount of repair, and are still in excellent 
order, but the time must soon arrive for replacing them by 
more powerful machines. 
In 1876 a series of trials was made by the Trinity House at 
the South Foreland, with various dynamo-electric machines, for 
the purpose of ascertaining the then most suitable machine for 
adoption at the Lizard. The results were decidedly in favour of 
the Siemens direct current machine, and machines of this type 
were accordingly installed at the Lizard Station in 1878. In 
consequence of irregularities in their working, and because, at 
the time, Baron de Méritens, of Paris, had perfected a very 
powerful alternating current machine, it was resolved to send one 
of the latter machines to the Lizard for trial, where it has worked 
most satisfactorily for several years. The experience gained at 
the Lizard suggested that, for the St. Catherine’s Station, where 
it had been resolved to adopt the electric arc light, the De 
Meritens machines should be employed, and they were accord- 
ingly ordered ; but, as arrangements were then being made for 
experiments at the South Foreland for testing the relative merits 
of electricity, gas, and oil as lighthouse illuminants, it was 
determined that these machines should first be sent there for the 
experiments. In 1862 a practical trial was made by the Trinity 
House at the South Foreland of the Drummond or lime light, 
but the results were not so satisfactory, after experience with the 
electric arc light, as to encourage its adoption. In the mean- 
time the successful development of the electric are light for 
lighthouse illumination very soon acted as a keen stimulus to 
inventors of burners for producing gas and oil luminaries for the 
purpose ; in 1865 the attention of lighthouse authorities was 
directed to the gas system of Mr. John R. Wigham, of Dublin, 
which system was tried in that year by the Commissioners of Irish 
Lights at the Howth Bailey Lighthouse, near Dublin, and in 
1878 he introduced at the Galley Head Lighthouse, county Cork, 
his system of superposed gas burners. At this lighthouse four 
of his large gas burners and four tiers of first-order annulzr lenses, 
eight in each tier, were adopted. By successive lowering and 
raising of the gas flame at the focus of each tier of lenses, he had 
previously produced the first group flashing distinction. This 
light shows, at periods of one minute, from ordinary annular 
lenses, instead of the usual long flash, a group of short flashes, 
varying in number between six and seven. The uncertainty, 
however, in the number of flashes contained in each group is 
found to be an objection to the optical arrangement here 
adopted. In the meantime the attention of the Trinity House, 
the Commissioners of Northern Lights, and the French light- 
house authorities was being directed to the question of substi- 
tuting mineral oil for colza as a lighthouse illuminant. In 
1861 experiments were made by the Trinity House for the 
purpose of determining the efficiency and economy of mineral 
oils in relation to colza for lighthouse illumination; but, owing 
to the imperfectly-renmed oil then obtainable and its high 
price, the results were not found to be quite so satisfactory as 
to justify a change from colza oil, at that time generally used. 
In 1869 the price of mineral oil, of good illuminating quality 
and safe flashing-point, having been reduced to about one-half 
the price of colza, the Trinity House determined to make a 
further series of experiments, when it was ascertained that, with 
a few simple modifications, the existing burners were rendered 
very efficient for the purpose, and a change from colza to 
mineral oil was commenced. It was found, during these ex- 
periments, that the improved combustion effected in the colza 
burners, in their adaptation for consuming mineral oils, had 
the effect of increasing their mean efficiency, when burning 
colza, 45} percent. A further advance was made during these 
experimei ts by increasing the number of wicks of the first-order 
burner from four to six, more than doubling the intensity of 
the light, while effecting an improved compactness of the 
luminary per unit of focal area of 70 per cent. 
With coal fires no distinctive characters were possible beyond 
the costly ones of double or triple lighthouses. There are at 
present not less than 86 distinctive characters in use throughout 
