;44 Mr. George K. B. Elphinstone ' [Felv 23, 



WEEKLY EVENING MEETING. 



Friday, Febrmiry 23, 1912. 



His Grace the Duke op Northumberland, KG. P.O. D.C.L. 

 LL.D. F.R.S., President, in the Chair. 



George K. B. Elphinstone, Esq., M.Iust.E.E. 



The Gyro static Compass and Practical Applications of Gyrostats. 



The employment of a moving body for the indication and control of 

 " direction " has occupied tiie attention of scientists for many years. 



In explaining what is meant by " indication " of direction, let the 

 subject be divided into two parts : — 



(1) Indication of direction, or measurement of angles in a vertical 

 direction. 



(2) Indication of direction, or measurement of horizontal angles, 

 such as in the case of a Compass. 



This property of moving bodies is a fundamental law, laid down 

 by Newton in his " First Law of Motion." " Every body continues 

 in its state of rest, or of uniform motion in a straight line, unless it 

 is compelled to change that state by external forces." 



As regards the use of Gyrostats, in order of date : — 



The measurement of vertical angles is of the first importance in 

 all navigation ; the height of the sun or other heavenly body above 

 the horizon furnishing a means for the determination of latitude 

 directly, and of longitude when used in conjunction with a means of 

 knowing Greenwich time. 



The earliest record of a practical application of a Gyrostat which 

 the lecturer has been able to trace is of the Gyrostatic Artificial 

 Horizon constructed by Mr. Searson in the year 1744. 



Mr. Searson submitted his invention to the Admiralty, and was 

 instructed by them to proceed for a cruise in H.M.S. " Victory." The 

 ship was lost with all hands, being blown against the rocks in a very 

 heavy gale otf Ushant in the year 1746. 



King George III. expressed considerable interest in Mr. Searson's 

 device, and the Commissioner of the Admiralty submitted some 

 sketches made by Searson to George Adams, an instrument maker of 

 Fleet Street, who constructed for King George III. in 1762 an exact 

 repetition of Searson's Gyrostat which was lost in the " Victory." 



This actual instrument is on the table, and can be shown at work, 

 owing to the kindness of the authorities of King's College, who have 



