THE experiments -with lighthouse illu- minants -which have been in progress at the South Foreland for twelve months, under a Committee of the Elder Brethren of the Trinity House, were brought to a conclusion in March last, and the Report was presented to both Houses of Parlia- ment in the form of a Blue Book, and published in August.

It has not been our fate to look into many Blue Books, and we fancy they often deserve their reputation of being very dry, and an uninteresting study. If so, this one is a good example of the old proverb, " The exception proves the rule," for it is in many ways a most interesting and, at the same time, instructive docu- ment, on a subject of the first import- ance, not only to ourselves, but to the whole maritime world. The first point that strikes us is the thoroughness of the work done, which was the natural out- come of the well-matured plans formed for carrying out the experiments. The scientific world was called upon to con- tribute its quota to the work in advice and assistance, which helped much to bring about the satisfactory results ob- tained. The co-operation of the Scotch and Irish Lighthouse Boards was invited and cordially given, and they, as well as the Board of Trade, were ably represented by their scientific officers.

The experiments were carried out with praiseworthy publicity, instead of with that unmeaning air of mystery which so often enshrouds experiments of -world- wide importance carried out by Govern- ment departments. Not only were mem- bers of scientific societies, especially those engaged in engineering, invited to inspect the arrangements, but tickets of admission were freely issued to the general public on application. Nearly every maritime nation in the world, including some of our Colonies, sent officers to visit the station, but of course our neighbours the other side the channel, from their position, were able to give most assistance by taking observations, &c.; and no doubt many useful hints were obtained from the ex- perts of other nations, -who -were always invited when they visited the station to give any suggestions that occurred to them.

The illuminants selected for competition were electricity, gas and mineral oil, each of which was displayed from wooden towers about 250 feet high, built at the South Foreland, near the powerful electric lights permanently exhibited there.

With the view, we suppose, of inter- fering as little as possible with the office of the permanent lights, and not to perplex passing ships, the experimental lights were only allowed to show through a section of the lantern extending northward, partly over the land and partly over the sea, and one to the southward over the sea. The powers of the different lights were tested scientifically by photometry, and prac- tically by the eye at marked distances, as well as from the neighbouring lightships, and by the masters and • pilots of passing vessels. The first-named method proved of little or no practical value, because it was found that the most distant stations erected for its use, rather less than two miles and a half from the towers, were too far off to admit of the light being measured by it. Under these circumstances, the only test to be relied upon was that of observation with the eye.

Upwards of six thousand of these obser- vations were taken at different stations, under varying conditions of weather, and by different observers, amongst whom were the Elder Brethren of the Trinity House and their officers on land and sea, which include the men on board the neighbouring lightships, and at the Ramsgate and North Foreland lighthouses, besides the different observing huts erected for the purpose; also the coastguard on shore, and a few by pilots and masters of vessels navigating the neighbouring waters. A complete and ingenious system was provided for register- ing their observations, founded on the assumption that the electric light was a standard, giving it the value of 100, and recording the relative values of the other two lights, by higher or lower numbers, as necessary, i.e., if the gas or oil was con- sidered only half as powerful as the standard, it was recorded at 50, and vice versa; if considered double as good, it would be marked at 200. Books prepared in the necessary form for recording these observations were widely distributed, in order to give every facility for marking the records. The outcome of these mea- sures was the receipt of upwards of six thousand returns, which had to be examined and scrutinised, with a view to decide their value for tabulation and analysis. This, itself, was no light work, and resulted in about two thousand being rejected, leaving four thousand on which to ground a decision.

Behind these general arrangements, there were, of course, many matters of detail to be carried out, which con- tributed, with equal if not greater im- portance, to the conclusive and satisfactory results sought for. Amongst these we may enumerate the height of flame, number of jets of gas or oil in a light, the number of electric lights or of currents, &c. The question of expense also had to be con- sidered, more particularly in proportion to the benefits to be derived from adopting the more expensive forms, either in new lighthouses, or instead of the cheaper systems at present in use.

The cost of establishing a first-class light- house with gas is computed at 20,5161., and its annual maintenance at 1,6S7Z.

An electric light of the same power would cost 17,749Z., and 1.927Z. per annum for maintenance.

A first-class oil-lighted station would cost 8,064Z., and the annual maintenance 724Z. Were no other considerations forth- coming, here alone is a very strong argu- ment in favour of oil, especially in these days of sad depression and " hard times " for the shipowners, on whom the expense of maintaining the lighthouse falls.

The general conclusions come to by the Committee, and the reasons upon which they are founded, will, we think, recom- mend themselves to all impartial minds.

They found that the electric light proved itself, under all conditions of weather, to have greater penetrating power than either of the others, but in clear weather it had such a dazzling effect at short distances, that it was very difficult to judge one's distance from it, and it is therefore very unpopular with seamen.

The Committee do not think it suitable for general adoption round the coast, but they consider that for bold headlands with great elevation, or those which con- stitute important landfalls for the mariner, it has great advantages.

The difference between the powers of gas and oil was found to be so slight as not to compensate for the extra cost both of installation and maintenance, and the inconvenience if not danger of the greater heat generated in the lantern by the former, added to which comes the con- sideration that all lighthouse-keepers in the service are now fully acquainted with the working of the oil lamps, and getting the best results out of them, but would not be for some little time with either of the other two lights. They therefore recom- mend mineral oil as the most suitable and economical medium for the ordinary nece's- sities of lighthouse illuminants, but for special places, such as salient headlands, important landfalls, &c., where a more than ordinarily powerful light is required, electricity offers the greatest advantages.