274 Proceedings, &c.,for 1886. 



Mr. C. W. M'Lean also read a paper on " Modern Marine 

 Indicator Diagrams." 



On the 26th May Mr. G. K. B. Steane read a paper on " The 

 CoUimation of Levels," which was discussed on the 30fch June. 



On the 25th August Professor Kernot read some notes on Mr. 

 J. A. L. Waddell's pamphlet on " Japan Railway Bridges," which 

 was discussed. 



On the 29th September Mr. C. W. M'Lean read a paper 

 on "Safety Valves," a brief extract from which follows: — 



" No safety-valve for steam boilers can be considered complete 

 unless it fulfils the following conditions : — 1. It must by its own 

 action prevent the steam pressure from rising more than slightly 

 above the working pressure to which it is loaded. 2. It must not 

 waste more steam than is absolutely necessary ; therefore it must 

 close when the pressure falls again to the working load. 3. It 

 must always be free to act efficiently without extraneous aid. 4. The 

 parts must be so closed in that they cannot be tampered with or 

 accidentally damaged. 5. For marine, locomotive, crane, and other 

 boilers it must be unaffected by motion or vibration. Lever- weighted 

 safety-valves gave place to dead-weighted valves regulated by the 

 Board of Trade rules. These, on account of never opening more 

 than 1-1 6 th of an inch, in turn gave place to spring- weighted 

 valves, now the most common for any but land boilers. The 

 improved valves, by reason of their lips, which are made to throttle 

 the steam after its exit from the boiler, and thus increase the area 

 of the valve acted on, lift more freely. The accumulation of pressure 

 rarely exceeds 10 per cent, when the fires are forced for 20 minutes." 

 Among many novelties and improvements mentioned, the steam- 

 loaded safety-valve invented by Mr. Alexander Wilson, of Melbourne, 

 is described. This valve's action, in the writer's experience, meets 

 the conditions of a perfect valve, set forth at the commencement of 

 the paper, in a more perfect manner than any other known. 



