TRANSACTIONS OF SECTION G. 795 



Automatic bell buoys, of various designs, and tbe Courtenay automatic whistling 

 buoy are found to render important aid to navigation in fogs, but, unfortunately,, 

 none of these apparatus have at present that reliabilitj^ which should be charac- 

 teristic of a coast signal, and all such buoys should be used with caution, owing to 

 their action being dependent on the motion of the sea surface. The remedy for this 

 defect is a problem which has yet to be satisfactorily worked out. 



Until very recently a beacon was known to the mariner as a day signal only. 

 Numerous structures, varying in form and dimensions, have for many years 

 occupied prominent positions on shore and on rocks and shoals at sea, in all the 

 maritime countries of the world, and some of these have been the work of con- 

 siderable labour and cost. The iron beacon on the Wolf Rock, off the west 

 coast of Cornwall, completed by the Trinity House in 1840, and which in 1870 

 was replaced by the present lighthouse, required, before the days of steam tenders, 

 five yeai-s to erect, and cost nearly 11,300/. The recent successful lighting of bea- 

 cons with automatic apparatus, in occasionally inaccessible positions, by electricity, 

 compressed mineral oil gas, and petroleum spirit, forms an important epoch in the 

 history of lighthouse illumination. In 1884 an iron beacon, lighted by an incan- 

 descent lamp and the current from a secondary battery, was erected on a tidal rock 

 near Cadiz. Contact is made and broken by a small clock, which runs for 28 

 days and causes the light to show a flash of 5 seconds, followed by a total eclipse of 

 25 seconds. The clock is also arranged for eclipsing the light between sunrise and 

 sunset. The apparatus is the invention of Don Isas Lavaden. 



In 1881 a beacon, lighted automatically by compressed oil gas, on the Pintsch 

 system, was erected in the river Clyde, and many other such structures have been 

 erected in this country and the United States. In 1881-82 several beacons, lighted 

 automatically by petroleum spirit on the system of Herr Lindberg and Herr Lyth, 

 of Stockholm, were established by the Swedish lighthouse authorities, and are 

 reported to be working efficiently. Last year a beacon lighted on this system, 

 and another lighted by Pintsch's compressed gas, were erected by the Trinity 

 House on the banks of the Thames, near Erith, and are found to be very 

 efficient aids for the navigation of the river by night as well as by day. The 

 petroleum spirit lamp burns day and night at its maximum intensity, and shows a 

 white light with a short occultation at periods of five seconds. The occultations 

 are produced by a screen, rotated around the light by the ascending current of 

 heated air from the lamp acting on a horizontal fan. As there is no governor, 

 the periods of occultation are subject to slight errors, but the gas beacon, 

 which shows a white flashing light at periods of two seconds, is provided 

 with a clock (specially designed for this beacon), which not only regulates 

 with precision the flashes and eclipses, but also extinguishes the light a few 

 minutes before sunrise and re-lights it just before sunset, a very feeble pilot light 

 being left burning during daylight. Arrangement is made in the clockwork for a 

 bi-monthly adjustment to meet the lengthening or shortening of daylight. These 

 two lighted beacons are in the charge of a boatman, who visits them at least 

 once a week, when he cleans and adjusts the apparatus, and cleans the lantern 

 glazing. These systems of lighted beacons are not yet sufficiently matured for 

 forming a decided opinion as to their relative efficiency and economy, but it maybe 

 considered certain that they will both be extensively adopted, because, in numerous 

 cases, for the secondary illumination of ports, estuaries, and rivers, automatic 

 lighted beacons can be installed to meet fairly the local requirements of navigation, 

 at a fraction of the first cost and annual maintenance of a lighthouse with its 

 keepers and accessories. 



In 1881 it was considered by the lighthouse authorities of this country that the 

 time had arrived when it was absolutely necessary that an exhaustive series of 

 experimental trials should be made, on a practical scale, for the exact determination 

 of the relative merits (both as regards efficiency and economy) of the three Ught- 

 bouse iUuminants, electricity, gas, and mineral oil, which, by the process of 

 natural selection, may be regarded as the fittest of all those at present knowi to 

 science. After many unforeseen difficulties had been overcome, this question of 

 universal importance was, in July 1883, referred by the Board of Trade to the 



