A Large Sunspot

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    Abstract

    THE rising solar activity continues to yield, amongst other phenomena, a fairly high frequency of sunspots about six groups a day being visible. These groups are usually of moderate extent, but about a dozen seen since the beginning of 1936 may be discriminated as naked-eye spots. These spots or groups of spots have areas of not less than 500 millionths of the sun's hemisphere or about 585 million square miles. The latest of these large spots is now crossing the sun's disk, from August 25 until September 6, with central meridian passage on August 30-7 U.T. Its growth to a large spot with multiple umbrae was considerable between August 27, when its area measured 400 millionths, and August 29, when it had increased to 900 millionths. The spot was surrounded by extensive faculae, as seen in integrated light, and by flocculi as seen in hydrogen light (Hcc) or in that of ionized calcium (H and K). There was marked activity recorded with the spectrohelioscope at the Royal Observatory, Greenwich, on August 27 and 28 in particular a bright eruption, visible in JQTp as well as in Hoc, on August 28 between 10h and h

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