ON A QUARTZ THREAD GRAVITY BALAXCK. 217 



stations in New South Wales, at Melbourne in Victoria, and at Hobart and Launceston 

 in Tasmania. On November 23rd, when hurrying to catch the train at Springwood, 

 N.S.W., out- <>C tin- handles <.f tin- lxx containing the balance broke, and one end of 

 the box fell through a distance of about two feet on to the asphalt platform. The 

 reading was found to be altered when we got to Sydney, but the thread was 

 undamaged. As the final result of the present investigation we have determined the 

 value of "gravity" at Hornsby, a station 21 miles from Sydney and 472 feet above 

 the laboratory, relatively to that at Sydney, in three journeys, with a maximum 

 difference less than one part in 500,000. For the purpose of a survey the evidence 

 shows that a single observation with the balance will enable g to be determined rela- 

 tively to a standard value to within one part in 100,000. There is a great probability, 

 however, that the error would be less than one part in 200,000. 



Before proceeding to the discussion of the subject of this paper we desire to perform 

 the pleasant duty of thanking those who have assisted us in one way or another, 

 and first amongst these is Mr. JAMES COOK, F.R.A.S., our mechanical assistant. 

 Mr. COOK made the whole of the instrument, except the thermometric appliances, 

 including his own working drawings from our sketch designs. It is not too much to 

 say that had we not been so fortunate as to have commanded his great mechanical 

 skill and accuracy we should in all probability have failed in our undertaking. 



To Mr. J. J. E. DURACK, Deas Thomson Scholar of the University of Sydney, and 

 to Miss FLORENCE MARTIN, we owe our thanks for much observational assistance. 

 Through the enlightened liberality of the Commissioners of the Railways of New 

 South Wales we were provided with free passes over the government railways. To 

 them, and to the Secretary for Railways, Mr. HUGH MAC-LACHLAN, we desire to 

 tender our tha*hks, not only for our free passes, but for the unfailing kindness and 

 courtesy which they showered upon us. 



Amongst those who have assisted us with advice upon special points we desire 

 especially to thank our colleague, Professor GUIINEY, Mr. G. H. KNIBBS, Mr. E. F. 

 J. LOVE, Mr. G. F. FLEURI, M. GUILLAUME, Mr. GRIFFITHS, and Mr. CHAKD, L.S. 



During our journeys we were provided with facilities for making our observations 

 by Professor LYLE, of the University of Melbourne ; Professor McAuLAY, of the Uni- 

 versity of Tasmania ; Mr. ALEXANDER MORTON, Curator of the Tasmanian Museum 

 at Hobart ; Mr. W. J. BAIN, of Launceston ; Sir PHILIP FYSH, (late) Premier of 

 Tasmania, and Dr. WlOAN, Acting Mayor of Armidale in 1897. 



The Surveyor-General of New South Wales also deserves our thanks for having 

 placed a disused theodolite at our disposal, the circle of which was employed for a 

 long time as part of our balance. 



BIBLIOGRAPHY. 



HERSCHEL. Outlines of Astronomy, Editions 1-4, Section 189 ; Edition 5, 



Section 223. 

 VOL. cxcin. A. 2 F 



