Portland Bill Lighthouse
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In August 1788 Argand lamps were installed, Portland being the first lighthouse in England to be fitted with them. In the upper or old house there were two rows, seven in each row, lighted with oil and furnished with highly-polished reflectors. Low light tests were made by Thomas Rogers with his new lens light, and six Argand lamps were installed, their lights increased by lenses.
In 1798, when Napoleon threatened invasion, two 18lb cannons were installed at the lighthouse.
A 7 meter tall white stone obelisk was built in 1844 at the Southern tip of Portland Bill as a warning of a low shelf of rock extending 30 metres South into the sea, which still stands near the current lighthouse.
New high and low lighthouses were built in 1869, but early this century Trinity House announced its intention of replacing them with a single tower - the present lighthouse. The old towers can still be seen from the outside - the low light, which is now a bird observatory and field centre, has retained its original appearance but the high light lantern has been removed.
A radio beacon with morse call-sign of PB transmits from the lighthouse on 309.50 KHz and has a nominal range of 50 sea miles.
The present optic at Portland Bill is very unusual as due to the arrangement of the panels the character gradually changes from one flash to four flashes between the bearings 221° and 224° and from four flashes to one flash between bearings 117° and 141°.
Portland Bill Lighthouse was demanned on 18th March 1996 when monitoring and control of the station was transferred to the Trinity House Operations Control Centre at Harwich. The automation of the lighthouse included replacement of the optic drive by a dual stepper motor system and the air fog signal by a directional electric emitter, controlled by an automatic visibility meter. A three position motor driven lampchanger ensures that failure of the main navigation lights automatically brings into operation an emergency lamp.
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HEIGHT OF TOWER HEIGHT OF LIGHT ABOVE MEAN HIGH WATER AUTOMATED OPTIC LAMP CHARACTER INTENSITY RANGE OF LIGHT FOG SIGNAL CHARACTER |
1716
41 METRES 43 METRES 1996 4 PANEL 1ST ORDER CATADIOPTRIC FIXED LENS 1 KW MBI WHITE GROUP FLASHING 4 TIMES 635,000 CANDELA 26 SEA MILES I 3,6 SECOND BLAST EVERY 30 SECONDS |