14 Proceedijigs of the Royal Society of Victoria. 



Conclusion. 



In the course of the observations, both here and in Sydney, a 

 curious circumstance presented itself, which seems to indicate a 

 peculiarity in the behaviour of the Shelton clock. Any very 

 rapid change in the barometric pressure always calls forth while 

 it is progress a change in the clock rate. As cases in point, the 

 observations of 30th January and 5th February may be cited. 

 On both these days the barometer fell rapidly during the first 

 series of observations, and the value of V is on 30th January 

 considerably higher for the second series than for the first, while 

 on 5th February the reverse is the case. When, however, no 

 sudden changes of pressure occur the difTerence between the 

 numbers obtained on the same day is always quite small. Can 

 this be a special property of gridiron pendulums % If so, the 

 following explanation may be tentatively suggested. Possibly, 

 owing to the friction between the rods, the geometrical form of a 

 gridiron pendulum normally lags behind the condition proper to 

 the actual temperature ; and the sudden changes of pressure may 

 act like slight shocks, enabling it to sudderily overcome this 

 friction. 



In concluding this paper I must express my gratitude to Mr. 

 Russell, who not only placed the resources of the Observatory at 

 my disposal, and aided me in the work in every possible way, but 

 also treated me with the greatest kindness and hospitality during 

 ray stay in Sydney. My thanks are also due to the members of 

 the Observatory staff, especially to Mr. Linehan, the chief 

 assistant, who took a great deal of trouble over the clock rates, 

 and helped me in other ways. Lastly, I would express my 

 obligations to the New South Wales Railway Commissioners for 

 their kindness in granting me a free pass over their lines. 



Appendix. 



On the Stability of the Stand on zvhich the Kaier Fenduhims 



are szuung. 



The copper cylinder in wliich the pendulums are vibrated, 

 together with the massive timber and iron framework which 

 carries it, was constructed at Dehra Dun for the Indian Trigone- 



