Memoirs of the Royal Astronomical Society Volume 19

Memoirs of the Royal Astronomical Society Volume 19

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1851 edition. Excerpt: ... advantage of this plan is, that the reservoir, receiving the first splash of the metal, avoids the risk of small portions being scattered over the iron base and becoming solid, before its surface is covered. I deem this method to he, on the whole, an improvement, though I did not succeed quite so well with it as with the other; I believe principally because the metal requires to be poured at a somewhat higher temperature to insure its remaining fluid until the surface of the base is covered. It is obvious that in this mode of casting, a failure must not be calculated upon, as the composition could not be remelted in the cupola without injury. ' As soon as the metal had become solid, it was conveyed by the crane (mould and all) into an annealing oven or furnace in a state of strong ignition. All draught to the furnace was then completely stopped, by luting up, and the metal and mould were covered with ignited cinders, closing the whole up ultimately with a tight cover. At the end of three weeks the speculum was taken out, and had not even then become perfectly cold. I very much doubt, however, whether this slow annealing process is absolutely necessary in specula cast on this plan. This speculum was ground and polished on a. machine almost precisely the same as that described by Lord Rossn, in his Lordship's very interesting paper published in the second part of the Philosophical Transactions for 1840. I found, however, the grinding process much facilitated by interposing a piece of sheet lead about a tenth or twelfth of an inch thick between the speculum and the iron grinding tool. This saved the rapid wearing down of the tool, and also cut the metal much faster, as the softness of the lead suffered the particles of emery to imbed...show more

Product details

  • Paperback | 114 pages
  • 189 x 246 x 6mm | 218g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236852745
  • 9781236852748