| RefNo | HSF/2/1/89 |
| Previous numbers | 32.8.72 and 32.8.72A |
| Level | Item |
| Title | Letter from J H [John Herschel], Bangalore [Bengaluru], to Major [James Francis] Tennant |
| Creator | Herschel; John (1837-1921); British army officer and astronomer |
| Date | 22 November [1868] |
| Description | Herschel cannot understand how he did not see a [spectroscopic] line near b. The three lines he did see were vivid and he had been trained by looking at nebula to recognise faint light. Solar physical theories and speculations are endless; they have some value, but the facts are so small that he will not speculate upon them. The simpest theory, of a complex atmosphere surrounding a hot mass of liquid or solid is enough of a working explanation. He discusses luminosity but concludes that 'The infinite possibilities implied in an unknown range of both heat & elementary constituents make it idle to speculate'. The solar atmosphere might be arranged in strata, but this is not likely. Herschel continues his discussion on luminosity, and as for the comet mentioned by Tennant, even less is known of cometary matter than solar ones. [Pierre] Janssen's idea [for observing prominences] is not a new one, and Herschel refers to his report to the Royal Society, which cites Captain Ronaldson's prism observation and Herschel outlines his own proposal for a heavy battery of prisms. For spectral analysis he thinks that achromatic lenses are a waste of power and a restriction of aperture, and gives his own suggested approach. On Tennant's theory of interplanetary spaces being occupied by 'ethereal hydrogen', he thinks it plausible, but notes difficulties, including the lack of knowledge on the properties of diffuse gas in such low temperatures as are supposed to exist there. He concludes by saying that he thinks Tennant has misunderstood Janssen's method, giving his reasoning. |
| Extent | 4p. |
| Format | Manuscript |
| PhysicalDescription | Ink on paper |
| AccessStatus | Open |
Fellows associated with this archive
| Code | PersonName | Dates |
| NA7955 | Herschel; John (1837 - 1921); Colonel; military engineer, surveyor and astronomer | 1837 - 1921 |