Page:Proceedings of the Royal Society of London Vol 69.djvu/251

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Total Eclipse of the Sun, 1901, May 18.
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"Total Eclipse of the Sun, 1901, May 18. Preliminary Account of the Observations made at Pulo Aoer Gadang, West Coast of Sumatra." By F. W. DYSON, M. A., F.RS., Sec. RA.S. Received October 24, Read at Joint Meeting of the Royal and Royal Astronomical Societies, October 31, 1901.

I. General Arrangements.

The Admiralty having approved of expeditions from the Royal Observatory to observe the Solar Eclipse of 1901, May 18, I was instructed by the Astronomer Royal to occupy a station on the West Coast of Sumatra with the instruments used at Ovar in the eclipse of 1900, May 28. Mr. J. J. Atkinson, who accompanied the Observatory expedition to Ovar, again generously volunteered his assist- ance and is associated with me in all the observations. His advice and co-operation were of the greatest value throughout.

The programme of observations, which was arranged in concert with the Joint Permanent Eclipse Committee, was essentially the same as that carried out at Ovar.

The 16-inch ccelostat and the 4-inch rapid rectilinear (Abney) lens were lent by the Royal Astronomical Society, and Captain Hills kindly lent the spectrosopic equipment he used at the Indian eclipse, viz., a two prism flint spectroscope, a four prism quartz spectroscope, and a 12-inch heliostat.

At the request of the Royal Society the Admiralty placed H.M. gunboat " Pigmy " at the service of the observers in Sumatra. We are indebted to Lieut, and Com. Oldham for the ready manner in which he assented to our request to anchor off Gadang, and let us live on the " Pigmy." Without his cordial co-operation this station could not have been occupied. We are further indebted to him and to the officers and men of the " Pigmy " for assistance in erecting the huts and instruments, and for the large share they took in the observations on the day of the eclipse.

We received every assistance from the Government of the Dutch East Indies in the choice of station and arrangement with the natives, and were given free passes for ourselves and instruments on the railways. We are specially indebted to Mr. Joekes, the Governor of the West Coast of Sumatra, to Mr. Von Locken, the Assistant Resident at Painan, to Major Miiller, the Director of the Ordnance Survey and Chief of the Dutch eclipse party, and to Mr. Delprat, the Director of Railways.

Itinerary. The observing huts and instruments having been despatched some days previously, the 16-inch cœlostat mirror and some of the photographic plates were taken to Southampton and put