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mountain regions the temperature falls below freezing point, and there are some high peaks which are eternally covered with snow. With increase in altitude the temperature decreases about 0°.5 Centigrade for the first 300 feet; the function is not linear, the decrease being more rapid at greater heights. The only reliable information that can be immediately deduced from the publications and records of the Koninklijk Magnetisch en Meteorologisch Observatorium te Batavia is that almost daily tropical showers will invade even the best observing stations available. Other sources of information have been principally private enquiries and observations made through the courtesy of Dr. Braak. Many helpful data have been found in "The rainfall of the East Indian Archipelago, Vols. 1, onwards, 1879-1919"; "Wind, weather, currents, tides and tidal streams in the Indian Archipelago," by J. P. Van de Stok; "Climate of the Malay Archipelago" by the same author, which will be found in the reports of the International Meteorological Congress held in Chicago in 1893.

Statistical investigations of the data available show that the cloudiness of the sky is in no way associated with the rise and fall of the barometer. Cyclonic and anti-cyclonic conditions do not exist in the Archipelago. The formation of clouds during the rainy season increases as the day proceeds, and seems to be influenced by local land and sea breezes, also the monsoons and, to a very large extent, by the height and direction of the mountain chains. The monthly rainfall records alone give absolutely no evidence whatsoever as to the suitability of a locality for an observing station. A heavy rainfall does not indicate a continuously clouded sky, but, on the contrary, it may be remarked that the tropical showers appear to be local and are quickly followed by sunshine, and during the rainy season, October to February, in Sumatra, the atmosphere is extraordinarily clear. The Malay Archipelago is perhaps the most volcanic region in the world,-in Java alone there are about 120 well defined volcanic centers, nearly 50 volcanoes, of which 20 are active.

During the drier season, May to August, the upper air over the southern region of Sumatra is contaminated with volcanic dust and haze, which are borne along by the southeast monsoon on its way from the dry interior of Australia, and then the astronomical seeing is impaired. In this connection one will probably recall the famous eruption of the island volcano, Krakatao, in 1883. On this occasion the amount of volcanic material hurled into the upper atmosphere absorbed much of the ultra-violet light in the sun's rays and was responsible for the very remarkable sunsets witnessed in the tropics for several months following the eruption. From this aspect it will be seen that the month of January has something to commend it.

In what follows we will endeavor to restrict our attention to the conditions along the eclipse path, beginning at the west coast of Sumatra, and subsequently working eastwards.

At Benkoelen the clouds which form as a result of local conditions

along the coast, are either quickly condensed in the neighboring mountains, or else borne along sooner or later by the light sea breeze. The rainy season in Sumatra is from October to February, but as the prevailing wind is northwest, slightly more rain is condensed on the western side of the Barisan Mountains than on the east. Alternating clouded skies, rain and sunshine are to be expected. The chance of a clear sky at the critical moment is an even one, and certainly much better than for stations on the other side of the mountains.

It should have been pointed out before that Tristi Island, which lies off the west coast of Sumatra, is just within the zone of totality, and although the duration will be very short, it might prove to be a valuable station for some branches of spectroscopic work. The weather conditions there would, no doubt, be better than on the coast near Benkoelen. So far as one can judge from data collected, inland stations are hardly worth considering. The monthly rainfall is about the same as elsewhere, but the rain falls less frequently, the hours of sunshine are less, and so the sky is likely to be overcast for correspondingly longer periods at a time, and thus the probability of favorably observing the eclipse is considerably lowered.

Place Padang Pontianak

Place Benkoelen

Palembang

AVERAGE PERCENTAGE OF SUNSHINE.

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.Year 65 65 69 71 76 69 72 73 57 64 57 61 67 47 58 59 62 62 68 69 63 53

PERCENTAGE OF SUNSHINE 8 A .M.-4 P. M.

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54 56 57 59

Feb. 1925

61

51

It appears that the only readily accessible place on the other side of the mountains, and, of course, near the center line and as far west as possible, is Palembang, a large scattered town with a population of about 53,000 inhabitants. It is situated in the low lying interior of the southeast, about 54 miles from the coast, on the River Palembang (sometimes called Musi). Palembang is quite an important place on account of the activities of the Royal Dutch Petroleum Company and the Government Coal Mines. It is also the terminus of the main line. of the South Sumatra Railway. This railway line runs right on to the wharves, and it is possible to load the trucks direct from ocean going steamers. The railway runs well into the highlands, but unfortunately all the villages it touches are well off the center line. There is also reliable motor transport service for passengers, mail and freight, which comes under the jurisdiction of the State Rail and Tramways. There are two splendid hotels at Palembang, "The Hotel Palembang" and "The Hotel Joling" and accommodation is easily obtained if due notice be given. Servants (jungus) for erecting the heavier parts of instruments and also bamboo shelters, could easily be secured. Building materials such as cement, bricks and timber can be obtained in any quantity.

We are led to believe, however, that the climate at Palembang is very debilitating, owing to the humidity and equable temperature, while the river vegetation and tropical jungle is infested with mosquitoes. The former would make preparations for observing the eclipse very trying, while the latter may menace the health of observers. Professor Ross* suggests sending a party to the vicinity of Palembang, but does not give any meteorological data or sufficient reason in support of his recommendation. Logically, Item 1 of his summary of the weather conditions, which our investigations fully confirm, namely, "that while at all stations the amount of cloud in the afternoon is greater than in the forenoon, the increase is less at the coast than at inland stations," indicates that it is not at all a good place. We find also that the duration of totality at Palembang is actually 8 seconds longer than the value given in the paper referred to above.

Penagen, a much smaller town, lies to the east of Palembang and is less inviting for the reason that it may be difficult to secure good accommodations, supplies and assistance.

Astronomical considerations do not warrant sending an expedition. or observing party further east than the west coast of Borneo.

In the shadow path, between Sumatra and Borneo, lies Banka Island -area, 4,460 square miles. The population consists mainly of Malay stock, about 60,000, and Chinese about 50,000; the latter being chiefly engaged in mining operations.

The chances of a clear sky at the critical moment seem to be slightly higher at Banka than at Palembang, or on the west coast of Borneo. Suitable observing stations might possibly be found on Third Point, Nangka Island, or near a village to the south of Mondo Bay, in Banka Strait, or a little south of Rangkalpinang, on the east coast. An objection to these places is, however, the stormy conditions generally prevailing in January, due to the change of the northwest to the southeast monsoon. The Koninklijke Paketvaart Maatschappij steamers, and also others, ply between Batavia, Rangkalpinang, Belinju, Montoc, and the small village on the south of Mondo Bay, but to get to Third Point or Nangka Island seems to present some difficulty.

Observing stations on the west coast of Borneo are not recommended, as they are exposed to the changeable weather during January, which is accompanied by storms in the Karimata Strait.

Apart from the better opportunities, astronomical and otherwise, seemingly afforded on the west coast of Sumatra, we are led to believe that scientists visiting Benkoelen will be well received and given every assistance. One would find the people there most hospitable, and living would be made extraordinarily easy. There is an up-to-date Eastern Hostelry in Benkoelen, and it would not be a difficult matter to secure accommodation on arrival. At Benkoelen, cement, bricks and building materials can be obtained in reasonable quantities. Benkoelen is an important place on account of the Government gold and silver mines.

*Monthly Notices of the R. A. S., Vol. LXXXIV, Page 662.

The Total Solar Eclipse of January 24, 1925

523

There are good automobile roads in the vicinity, and it is easily possible to reach the center of the moon's shadow. It possesses a safe harbor and there is a frequent steamer service to and from Batavia, maintained by the Koninklijke Paketvaart Maatschappij.

Melbourne University, June 1, 1925.

THE TOTAL SOLAR ECLIPSE OF JANUARY 24, 1925.
Observations Made at East Chop Light Station,
Martha's Vineyard, Mass.

By ELEANOR A. LAMSON.

With the intention of obtaining a photograph of the outer extensions of the corona during the solar eclipse of January 24, 1925, the Naval Observatory sent one of the 6-inch Dallmeyer portrait lenses, of 38inch focal length, to Martha's Vineyard, Mass., in charge of Miss E. A. Lamson of the astronomical staff.

The time was limited, Miss Lamson being detained in Washington until January 20, and consequently a large amount of work had to be done after her arrival at the Eclipse Station in the short period of three days. Fortunately Prof. G. W. Rolfe, whose home is on the Island, rendered all possible assistance, and to him and to his wife the writer is most deeply indebted.

The lens in its brass tube, together with the necessary drawings for camera boxes, was sent to the Vineyard in care of Professor Rolfe. He received the lens January 17 and had the boxes made by the time. Miss Lamson arrived on January 21. The camera was then completed and an equatorial mounting of pine timber to support it was constructed, with a fairly heavy portable base to give stability on the frozen, snow-covered ground. To hold the photographic plates an ingenious, hand-driven plate carriage, to be timed for following the sun by means of a metronome, was attached to the "eye" end of the camera box. This device was made at the Observatory, for the writer, from plans by and under the direction of Mr. C. B. Watts of the astronomical staff, and proved to be most satisfactory in action.

A preliminary photographic focal length of the lens was determined on the cloudy, blustering night of January 21 by exposing 5 by 7 Eastman Speedway plates on the distant lights across the Haven. Check plates were made the following night by star trails, pointing on Polaris and using double-coated Eastman D-C Ortho 5 by 7 plates.

Before leaving Washington, at the suggestion of Mr. G. W. Purdy, the Keeper of the Light Station at East Chop, it was decided to use the Light Reservation for the eclipse work, Mr. Purdy having obtained permission for this purpose from the District Superintendent of Lighthouses at Boston. This was a most happy decision since the latitude and longitude of the Light were available at Washington and conse

quently the times of contact and duration of totality could be computed in advance.

[graphic]

Fig. 1.-The camera and mounting as used during the Total Solar
Eclipse of January 24, 1925. East Chop Light Station,
Martha's Vineyard, Mass.

Upon visiting the reservation a satisfactory site for the camera was found on the high bluff 122 feet E by N1⁄2 N from the center of the light tower and near the small, white brick oil-house which would serve as a wind break. The coördinates of the light tower as given by the Coast and Geodetic Survey are as follows:

Latitude =+41° 28' 13:139

Longitude =

= 70° 34' 4"573 West from Greenwich.

Near the camera and also sheltered from the wind by the wall of the oil-house a location was found for the 24-inch Tolles telescope, the

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