TRANSACTIONS OF SECTION A. 437 



Commissioners of Irish Lights. The light was so powerful as to enable the British 

 Association programme to he read at a distance of about six miles. 



III. A Mode of Lighting Sea Beacons from a Position on Shore. 



The author pointed out the convenience of using gas for this purpose, and 

 noted the arrangement by which this is done. Difficulty of maintaining small 

 lights at low pressure. A series of beacon or harbour lights may be maintained 

 by this plan, the initial pressure on shore being about six inches. Thus the lights 

 would be raised by turning off the gas, and lowered by turning it on. To illustrate 

 this, lights in various parts of the lecture room controlled in this way from the 

 lecture table. 



11. A Short Description of two hinds of Fog Signals* 

 By J. R. Wigham, M.R.I.A. 



I. Gas Guns as Fog Signals. 



The author mentions the importance to navigation of audible fog signals, ajid 

 origin of gas guns. The important peculiarity of this mode of fog signalling, is that 

 the gun may be placed on an isolated rock at sea, probably inaccessible in most 

 weathers, and perhaps almost too small to hold an ordinary gun, and charged and 

 loaded from a position on shore. The gas gun is unaffected by the action of water. 

 As a practical illustration a small gun was fixed in the College Park, and charged 

 and fired from the lecture room. The sound of the gas gun was equal to that of 

 an 18 pounder. The flash of the gas gun is very useful as a fog signal, being more 

 vivid than that of gunpowder. 



II. The Irish Siren Fog Signal. 



The United States Lighthouse Board was the first to introduce the Siren as a 

 fog signal. The author alluded to the action of Dr. Tyndall and the Trinity 

 House, Sir William Thomson and Sir Richard Collinson. The Irish Siren is less 

 complicated and less cumbrous than those heretofore used. An Irish Siren was 

 exhibited on the lecture table, and sounded at the conversazione of the Royal 

 Dublin Society on Thursday, the 15tb inst. 



12. A New Atmospheric Gas Machine. By J. R. Wigham, M.B.I.A. 

 The author exhibited one of these machines, and explained his invention. 

 * Published in extenso in ' Engineering ' of August 23, 1878. 



