538 SEC.- 12, APPLIED MECHANICS. 



2201. Model of the Lamlash Lighthouse Apparatus, 



showing the new twin prisms for preventing the loss of light by 

 absorption, and for saving room in the lighthouse, lately described 

 by Mr. Thomas Stevenson in " Nature," which are now for the 

 first time being ^constructed, and the new back prisms first intro- 

 duced at Lochindaal Lighthouse, in Islay in 1869. 



The Commissioners of Northern Lighthouses. 



220 la. Revolving Light, with Fresnel Apparatus, con- 

 densing lenses, and electric lamp, J 876. 



Sautter, Lemonnier, Co., Paris. 

 It is proposed to use this light on Cape Grisnez, near Calais. 



2201b. Catadioptric Light, with " projector " apparatus 

 and electric lamp, 1876. Sautter, Lcmonnier, fy Co., Paris. 



This apparatus is designed to throw or "project" a flash of light seaward 

 at certain intervals of time, or at will. It is fitted with mechanism for the 

 purpose of varying the altitude and azimuth of the beam of light projected 

 towards the sea, so as to ensure the utmost effect in all states of the atmo- 

 sphere. 



2202. Lighthouse Apparatus. 



1. Lens with Echelons. 1st essay. Fresnel, inventor, 1819. 



2. Polygonal lens, of the first order. Do. ! do. 1820. 



3. Annular lens, of the first order. Do. do. 1821. 



4. Apparatus for fixed lights. Do. do. 1824. 



5. Apparatus with catadioptric rings. Do. do. 1825. 



6. Lens with catadioptric rings, constructed in . 1825. 



7. Model of apparatus with catadioptric rings. Fresnel, 1825. 



8. Burner with 4 wicks, constructed after experiments 



made by Arago and Fresnel in . . . 1820. 



9. Burner with 2 wicks, with external covering, by 



Henry-Lepaute ..... 1845. 



10. Burner with 4 wicks, storied, for mineral oils. 



11. Large annular lens of Barbier and Tenestre . 1867. 



12. Lenticular panel for flashing lights of Henry-Lepaute 1 876. 



13. Apparatus for revolving electric lights, of Sautter, 



Lernonnier, & Co. .... 1876. 



Lighthouse Service of France, Paris. 



Echeloned Lenses. 



No. 1. First essay of echeloned lens, polygonal form. Invented by 

 A. Fresnel, and constructed under his direction in' 1819. 



No. 2. First echeloned lens, polygonal form, for flashing lights of the first 

 class. Invented by A. Fresnel, and constructed in 1820. 



No. 3. First echeloned lens, annular form, for flashing lights of the first 

 class. Invented by A. Fresuel, and proceeding from the lenticular apparatus 

 on the tower of Cordouan in 1821. 



When Fresnel conceived the idea of substituting in lighthouses large glass 



