4 58 SEC. 12. APPLIED MECHANICS. 



and completed in 1759, by Smeaton, F.R.S., civil engineer. This 

 original model, made by Smeaton, was sent by royal command for 

 the inspection of His Majesty George III. and the Royal Family, 

 and has since then remained in the possession of Mr. Smeaton's 

 family. 



Mrs. Croft Brooke. 



2203a. Model of the Lighthouse on La Corbiere Rock, 

 Jersey. Sir John Coode. 



The first lighthouse constructed in concrete ; tower erected in 1874. Sir 

 John Coode, engineer. Modelled by Mr. Joseph Thomas. Scale, y^ of 

 natural size. 



2203b. Parabolic Reflector, rendered holophotal, accord- 

 ing to Mr. Thomas Stevenson's design, by being fitted with a lens 

 and reflecting prisms, and a portion of a spherical mirror, so as to 

 parallelise all the light of the lamp. Introduced in 1849. 



The Commissioners of Northern Lighthouses. 



When the apparatus is to be cleaned the lamp is lowered out of the 

 reflector on a sliding carriage, as arranged by the late Mr. Robert Stevenson, 

 in 1814. The object of the sliding carriage is to insure the return of the 

 burner to the proper focus. 



2204. Model of First-class Fixed Dioptric Light. This 

 apparatus consists of a central lenticular band, and an upper and 

 lower set of reflecting prisms. The cylindrical belt, with diagonal 

 joints, and the upper and lower reflecting prisms, were substituted 

 by Mr. Alan Stevenson, in 1836, Jfor the segmental belt and upper 

 and lower silvered mirrors of Fresnel's first-class apparatus. 



(One-fifth of full size.) 



The Commissioners of Northern Lighthouses. 



2205. Model of Fourth Order Dioptric Condensing 

 Apparatus for Lamlash Lighthouse, showing the twin prisms, 

 1875. (One-half of full size.) 



The Commissioners of Northern Lighthouses. 



2206. Model of Mr. Thomas Stevenson's Marine Dyna- 

 mometer, for ascertaining the force of waves during storms. The 

 greatest force recorded in the German Ocean was 3J tons per 

 square foot. Messrs. D. and T. Stevenson. 



2207. Drawing of Storm Curve, showing the genesis of 

 waves illustrative of Mr. Thomas Stevenson's formula A=l'5\/j), 

 where 7i=height of wave in feet, and D= length of fetch in miles. 



Messrs. D. and T. Stevenson. 



2208. Drawing illustrative of formula for the reductive power 

 of harbours. Messrs. D. and T. r Stevenson. 



