278 Mr Russell on a Marine 8alino7neter for indicating the 



contracted to about a third part of its breadth, by leaves moved 

 forward for the time, as represented by R S on the plan, or 

 otherwise. 



A narrow projection immediately before any opening, if 

 necessary, prevents the light within from being seen in front. 



The box is white within, to reflect light. 



T M, T L, on the Plan, tubes for gas (the latter consisting 

 of one of the supports of the lantern, hollow), supplied, when in 

 use, by inserting the nozle of a flexible tube at T, or other- 

 wise. 



U, V, stop-cocks moved by levers attached, which are closed 

 by springs and opened by cords extending to the front. The 

 levers have checks adaptable to the variable pressure of the 

 gas, for example, linen threads attached to pins turning in the 

 board, so that either flame, when not required, may be reduced 

 to a blue point. The levers and springs are made to fold back 

 upon the board when not in use. 



The arrangement now shortly described is given merely as 

 a specimen. The details of any diorama made upon this prin- 

 ciple of construction, for example the description, number and 

 position of the lights, will, of course, be adjusted according to 

 the judgment of the maker, and will be modified by the size 

 of the apparatus and other circumstances. 



G. Tait. 



Edinburgh, 2d January 1843. 



Description of a Marine Salinometer for the purpose of indi- 

 cating the Density of Brine in the Boilers of Marine Steani- 

 Engines. Invented by J. Scott Russell, M.A., F.R.S.E., 

 F.R.S.S. A., Civil Engineer. (With two Plates.) Commu- 

 nicated by the Royal Scottish Society of Arts." 



It was very early in the history of steam navigation that 

 the inconvenience of raising steam from salt water was ex- 

 perienced. When the Comet descended below Port-Glasgow 



* Read before the Royal Scottish Society of Arts 28th February 1042, 

 and the Honorary Silver Medal of the Society awarded 14th November 1842. 



