Adams, — The Wellington Tide-gauge. 



407 



clusively used in India is that known as Newman's pattern, in which the 

 drum is horizontal, the only exception being a small gauge at Prince's Dock, 

 Bombay, where the drum is vertical." 



Full details of the Indian gauges are given in vol. xvi, while a description 

 of the Newman gauge is also given in Baird's Manual.* The horizontal 

 drum of the Newman gauge is 5 ft. 3 in. long, and exactly 21 in. in circum- 

 ference. The drum revolves by clockwork once a day, and has attached 

 to it the record-paper. A pencil moves in a slide along the top of the drum, 

 and to the pencil-carriage a wire is attached which is actuated by the float 

 through cog-wheels. In this arrangement there are many defects : " First, 

 the drum for the diagrams was not quite circular in section, the ellipticity 

 in some cases being very marked. Secondly, the drum was not stable in 

 every position of its revolution — i.e., when disconnected from the clock and 

 turned by hand it assumed a certain position of its own accord." 



To overcome the first defect it was necessary to make the clerk in charge 

 mark the exact position of the pencil on the diagram at four different times 

 of the day, then to redivide the diagram from these marks. Thus the whole 

 advantage of a ruled diagram was lost, as also many of the advantages of 

 a self-registering gauge, as constant attention of the clerk in charge is 

 required. The second defect was ingeniously overcome by a special back- 

 lash w^eight. There were many other defects, particularly in the adjust- 

 ment of the drum in relation to the clock, and to overcome all these defects 

 so many additions were necessary as to render the gauge a complicated piece 

 of mechanism requiring skilled attention. 



In the Indian gauges constant attention is required to prevent the error 

 of the clock becoming serious. The duties of the clerk in charge of an 

 Indian tidal observatory involve constant attendance at 7 and 10 a.m. and 

 4 and 6 p.m. daily, and where labour is cheap (£2 to £2 10s. per mensem) 

 this attention can be easily arranged for ; but in other parts of the w^orld 

 gauges requiring less attention are necessary. 



Fig. 1. 

 (Scale, l,OOO.ft. to an inch.) 



The Wellington tide-gauge was designed by Mr. William Ferguson, M.A., 

 M.Inst. C.E., formerly Engineer and Secretary to the Wellington Harbour 



*"A Mamial for Tidal Observations," by Major A. W. Baird. London: Taylor 

 and Francis, 1886. 



