Sir William Herschel / A.R. Hinks.

  • Hinks, Arthur R. (Arthur Robert), 1873-1945.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Sir William Herschel / A.R. Hinks. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    of discovery with such instruments as he could construct from the materials then obtainable. Let us glance at the state of telescope-making at the time, that we may the better appreciate the difficulties he had to face. It was an age of stagnation in telescopic discovery. Progress with the refracting telescope had been checked for nearly a century by the extreme difficulty of manipulating the long instruments with a single lens for objective. The achromatic objective had been invented ; but the impossibility of procuring the necessary discs of flint glass had delayed its coming into use, and it is improbable that in 1773 an achromatic objective of more than two inches aperture could have been bought. In the course of the eighteenth century some progress had been made in the construction of reflecting telescopes after the models of Newton and of Gregory; opticians such as Hearne or Short were able to supply instru- ments of apertures up to about six inches, though doubtless at a high price. These were useful instruments of their kind; and we think that if Grant was right in saying that no discovery had ever been made with the reflecting telescope, the fault lay not so much with the opticians as with the observers, who lacked the courage really to try what could be done with them. The faculty of telescopic discovery is in truth one of the rarest of faculties ; for just as no one had possessed it in any marked degree in the twenty or thirty years before the time of Herschel, so not one of those who in after years bought telescopes made by him succeeded in doing anything considerable with them. Herschel’s early attempts at telescope-making were directed to the building of a refractor on the Huyghenian plan, as is evident from the purchase of the object glass of ten feet focal length, and from the account given by his sister of her making tubes of pasteboard, which were too weak and were replaced by tin. A few weeks’ experience of the inconvenience of these long unrigid tubes showed that little could be done until the instrument was made more manageable by shortening it. When there was no possibility of getting an achromatic objec-1 tive, his thoughts, guided by Dr. Smith’s celebrated treatise on Optics, turned naturally to the idea of a reflecting telescope. We learn from his sister that he wrote to enquire the price of a reflecting telescope of seven feet, that is to say, with an aperture of about six or seven inches ; but the price asked was so much