But indeed at that early time all lights had not even the advantage of the glazed lantern which protected the candles of the Eddystone from the winter’s blast and summer’s breeze; the grand Tour de Cordouan on the coast of France was then lighted by blazing fagots of wood burned in an open chauffer, and many of the early lighthouses were open coal fires.
When Mr. Smith, however, was appointed Engineer to the Scotch Lighthouse Board, he, as has been already said, came forward as the advocate of lamps aided by reflectors, a system which he introduced at Kinnaird Head in 1787; so that the Lighthouse Board of Scotland never employed any less perfect mode of illumination. These early reflectors, which had been in use in England, consisted of small pieces or facets of common mirror glass arranged in a hollow mould and fixed in their places by plaster of Paris; but soon afterwards the facets of mirror glass, though forming good instruments for their day, and of their kind, were discarded, and the reflectors were thereafter made of copper, plated with silver, and brightly polished.
I am not in a position to say when or by whom these metallic reflectors were first introduced, or what was their exact form, the question being invested in some degree of doubt; but it was to the perfecting of these optical instruments and adapting them to practical use in a lighthouse that Mr. Stevenson’s attention was early directed. Thus we find him in 1805 reporting as follows:—
“The operations at the Start Point were this season begun upon Monday the 27th of May, and the lighthouse was finished upon Saturday the 17th October and the light advertised to be lighted upon the night of Wednesday the 1st of January 1806. Some nights before I left Sanday I had the light set in motion, when the effect appeared to be most excellent; indeed, it must be equal to the Scilly or Cromer lights, and superior to the revolving light at Tinmouth: at the former there are twenty-one reflectors, and at the latter there are fifteen, whereas at the Start Point Lighthouse I only use seven reflectors, but by altering the motion of the machinery and construction of the revolving part, I produce the desired effect.”
And again in 1806:—
“I was late in the season for making all the observations I could have wished upon the Start Point and North Ronaldsay lights, and was not very well appointed in a vessel for keeping the sea in bad weather. I however made a cruise for this purpose, and stood towards the Fair Isle in a heavy gale of wind, with an intention to run for Shetland, but the wind shifted, and I stretched towards Copinshaw, at the distance of about ten or twelve miles to the westward of Orkney, with both lights in view. The second night I went through North Ronaldsay Firth to have a west view of the lights. I put about off Westra, and stood northward with both lights in view, when it came to blow with great violence from the s.w., and it was with much difficulty we could regain the coast. Although on this trip I had rather bad weather, with a heavy swell of sea, yet it was very answerable for my purpose, and I was upon the whole much pleased with the appearance of the new light; but I find, when at the distance of ten or twelve miles, with the sea running high, the light is seen for rather too short a period, so that it would be proper to place other seven reflectors upon the frame at an angle of about 40° to the present reflectors, in the event of removing North Ronaldsay light.”
I find from his correspondence that my father consulted Sir John Leslie, the distinguished Professor of Natural Philosophy, and Alexander Adie, the well-known optician, as to the best mode of procuring a true parabolic form for the construction of his reflectors, and having introduced a simple means of withdrawing the lamp from the reflector, his new catoptric apparatus may be said to have been completed.
Fig. 4.
