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 Docek, 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 24 in. in circumference. 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 sell-registering gauge, as constant attention of the clerk in charge is required. The second defect was ingeniously overcome by a special backlash weight. There were many other defects, particularly in the adjustment 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 world gauges requiring less attention are necessary.

FIG. 1. (Scale, 1,000 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

Board. It was erected in 1887, and is at present situated in N shed, on Jervois Quay, Wellington, as shown in fig. 1.

The general design of the gauge is shown in fig. 2. The cylinder or drum is 4 ft. long and 0.4 ft. in diameter.^* It is horizontal, and carries a wheel 2.4 ft. in diameter on the end of its axle. The float is attached by a band to the circumference of the wheel. A smaller wheel carries a counterweight to keep the float-band always taut. The pencil-carriage moves horizontally at a uniform rate, and is in train with the driving-chain of the eight-day lever clock. Its motion is approximately 6 in. a day, so that one week's record is obtained on the drum.

It will be seen that the design of this gauge avoids all the defects of the Newman and other forms of gauge. Thus, owing to the smaller diameter of the drum, it can be readily turned truly circular, and, as it is the amount of motion under the pencil that has to be measured, small ellipticity of

Fig. 2.—The Wellngton Self-Registering Tide-Gauge.

section does not vitiate the record, and, although the drum is naturally turned as evenly as possible, any defect in balancing is immaterial, as the counterweight can be adjusted to overcome it. It is, however, in the adjustment of the time that the greatest improvement becomes apparent. The clock is wound up once a week, and when wound up the pencil-carriage is drawn to the left end of the drum. A new record-paper is attached to the drum, which is then revolved underneath the pencil, and on the line so drawn the correct local mean time is written, independent of what time is shown on the clock. At the end of the week the drum is again turned round,