446 SEC, 12. APPLIED MECHANICS. 



2182. Model of a Lighthouse now building upon the Little 

 Basses Bock, part of a reef about 7 miles S.S.E. of the coast 

 of Ceylon. Trinity House, London. 



The tower is of Scotch granite (Dalbeattie), each stone of which was 

 dressed, fitted, and marked in this country, freighted to Galle, and thence 

 carried to the rock and fixed in its place. The light is intended to be of the 

 first order, dioptric, on the group-flashing principle, showing two flashes in 

 quick succession every minute, at an elevation of 1 10 feet above high- water 

 spring tides. 



The rock is awash at low water, and is exposed to heavy seas during both 

 the N.E. and S.W. monsoons, and while the latter prevails is inaccessible 

 for work. The drawings show the methods of landing stone in a seaway by 

 steam-power. 



This lighthouse, as well as its fellow on the Great Basses just completed, is 

 building from designs by James N. Douglass, M.I.C.E., under the super- 

 intendence of William Douglass, M.I.C.E., for the Corporation of Trinity 

 House, London, acting on behalf of the Home and Colonial authorities. 



Its cost is estimated at 73,OOOZ., and completion is anticipated within five 

 years from date of commencement. 



2182a. Lantern and Apparatus intended for the Little 

 Basses Lighthouse, Ceylon. Trinity House, London. 



The lantern is of the cylindrical type adopted by the Trinity House, its form 

 gives maximum strength, and secures greater optical accuracy than the earlier 

 methods of flat glazing. The gun-metal framing is inclined about 30 from 

 the perpendicular, and is helically curved throughout, thus reducing to a 

 minimum the obstruction offered to the light sent forth from the lenses. 



The optical apparatus, constructed upon the group-flashing principle, 

 designed by J. Hopkinson, B.A., D.Sc., at the glass works of Messrs. 

 Chance Brothers, is the first dioptric instrument of its kind adopted by the 

 British lighthouse authorities. It is 12-sided, and makes a completed revolu- 

 tion in six minutes, so that the panels being arranged in pairs, a double-flash 

 meets the eye of the observer once a minute. 



The lantern and apparatus prepared for this structure are exhibited in 

 working order in the grounds outside the Museum. 



2183. Drawing of a Light Vessel with deck plans showing 

 internal arrangements and disposition of Syren Pog Signal 

 machinery. Trinity House, London. 



The hull is designed after that of the vessel now at South Sand Head 

 (Goodwin), built last year, of about 212 tons, and fitted with a syren fog- 

 signal, giving one blast every two minutes, by means of compressed air, at a 

 pressure of 30 Ibs. to the square inch, the apparatus being driven by a caloric 

 engine, which also works the windlass. 



The illuminating apparatus represents that in use at the Royal Sovereign 

 Shoal, off the coast of Sussex ; it is catoptric, and is upon the " group-flashing " 

 principle, giving three flashes in quick succession every minute. The crew 

 space is for seven men, including the officer in charge. The hollow iron 

 mast affords access to the lantern, and allows of the lamps being trimmed in 

 all weathers without danger of extinction. 



2184. Two Syrens, each a portion of the present First 

 Class Pog Signal, and a diagram showing the method by which 

 they are put in action. Trinity House, London. 



