Record

HSF - Correspondence of Sir John Frederick William Herschel, and the Herschel family
- 2 - Correspondence of Colonel John Herschel
  - 1 - Letters of John Herschel to Margaret Brodie Herschel and John Frederick William Herschel

RefNo	HSF/2/1/97
Previous numbers	32.8.81
Level	Item
Title	Letter from J H [John Herschel], Bangalore [Bengaluru], to 'Dear Father' [Sir John Frederick William Herschel]
Creator	Herschel; John (1837-1921); British army officer and astronomer
Date	12-15 June 1869
Description	He has little time to devote to detailed description and therefore sends a sketch of what he observed this morning, having seen many more but none so distinctly. He can only devote one hour each morning to viewings. He describes the slit view of a monochromatic image of the Sun's chromosphere, with a segment of the true limb. He notes two classes of 'solar cloud' here, one fleecy and one well defined. He gives further comments on the picture, which is pasted onto the letter [on p.3] seen on 'a back ground of pretty strong solar spectrum; and vertical streaky light...just short of dazzling'. A large group of spots was visible within the limb. The universality of the hydrogen envelope is now beyond dispute, he thinks. He discusses the absorption lines and the variability of the C line noted in a previous letter of 10 May. He believes these corresponded with the penumbra of a spot group, giving a second illustration of a slit view across the edge of the solar disc and corresponding spectrum lines. Faculae were observed between group and the limb, and the observation repeated on 11 June, while today, the spot was 'round the corner'. No other spot was decidedly seen, but the suppression of the dark line has been suspected elsewhere. Today, he detected that bright accumulations on the disc, faculae, give a continuous spectrum. He describes his observations and the difficulties in identifying the exact source of the light, but in one case it was certainly from a facula. He lists three facts that require explanation. [From 15 June] A number of 'Scientific Opinion' has arrived, with a notice of a paper by [J Norman] Lockyer, showing that John is two months behind. However the sights are so beautiful that no other incentive is needed. He showed a solar prominence to Mary who said that his sketches did not do them justice. He is using the Royal Society's instrument as fitted up for the eclipse, but with the dispersion increased threefold, using compound prisms extracted from hand spectroscopes. He describes their arrangement and thinks he can further increase the dispersion. The arrangement bars him from the violet end of the spectrum and he will one day become impatient and rearrange the apparatus with this in mind. He wishes he had more time to write on the subject but it is enough to put others in track. He hopes Alick [Alexander Stewart Herschel] takes an interest in these things. The packet of Proceedings arrived that day. With a brief postscript from Mary Cornwallis Herschel.
Extent	8p.
Format	Manuscript
PhysicalDescription	Ink and coloured chalk on paper
AccessStatus	Open

Fellows associated with this archive

Code	PersonName	Dates
NA7955	Herschel; John (1837 - 1921)	1837 - 1921

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