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Honor is like that glassy bubble,
That finds philosophers such trouble:
Whose least part crack'd, the whole does fly,
and wits are crack'd to find out why?
(Note: The figure referred to in the author's account which follows, is not provided. You will have to use your imagination.)
"The drop, or bubble, mentioned in this simile, is made of ordinary glass, of the shape and about twice the size described in the margin. It is nearly solid. The thick part, at D or E, will break the stroke of a hammer; but if you break off the top in the slender and sloping part at B or C, the whole will burst with a noise, and be blown about in powder to a considerable distance. The first establishers of the Royal Society, and many philosophers in various parts of Europe, found it difficult to explain this phenomenon. Monsieur Rohalt, in his Physics, calls it a kind of a miracle in nature, and says, (part i.c.xxii. Paragraph 47:) Ed. Clarke lately discovered, and brought it hither from Holland, and which has traveled through all the universities in Europe, where it has raised the curiosity, and confounded the reason of the greatest part of the philosophers:? He accounts for it in the following manner. He says, that the drop, when taken hot from the fire, is suddenly immersed in some appropriate liquor, (cold water he thinks will break it,) * by which means the pores on the outside are closed, and the substance of the glass condensed; while the inside not cooling so fast, the pores are left wider and wider from the surface to the middle: so that the air being let in, and finding no passage, burst it to pieces. To prove the truth of his explanation, he observes, that if you break off the very point of it A, the drop will not burst: because that part being very slender, it was cooled all at once, the pores were equally closed, and there is no passage for the air into the wider pores below. If you heat the drop again in the fire, and let it cool gradually, the outer pores will be opened, and made as large as the inner, and then in whatever part you break it, there will be no bursting. He gave three of the drops to three several jewelers, to be drilled or filled at C, D or E, but when they had worked them a little way that is, beyond the pores which were closed they all burst to powder."
* Here he is mistaken.(editor's note in the reference that follows.)
Comment: The letters refer to points along the drawing of the drop which is shaped like a tadpole, i.e., a large bulbous head and an extended tail. The drawing and notes are by Rev. Treadway Russel Nash, D. D. in Hudibras, Part II Canto II, lines 380. 1793.
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Zachary Grey in his notes and preface to Hudibras did not comment on Prince Rupert's Drops.
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Robert Rupert (1619-1682) Bavarian prince. Fought with Charles I, won some battles, lost some. Escaped to Europe during Cromwell's ascendency. In Paris involved in scientific studies where he developed a metal a brass alloy which is called "prince's metal" and glass drops known as "Prince Rupert's drops". Returned with Charles II to England. First governor of the Hudson Bay Country, a territory in a part of the Northwest Territory is named after him - Rupert's Land.
The Standard Reference Work, Volume V, Chicago, Progressive Educational Society, 1913.
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Called scientific toys. Drops of molten glass are thrown into water where they suddenly consolidate. They have an unusual shape similar to a tadpole. The larger end may be hammered on an anvil without breaking, but if the smallest fragment is nipped off the tail the drop explodes with violence. The phenomenon is due to the state of strain in the interior of the mass of glass, caused by the sudden consolidation of the crust. The crust is formed while the internal mass is still liquid. This tends to contract on cooling, but is prevented by the molecular forces which attach it to the crust. It is, therefore, somewhat in the state of the dog-head of a gun on full-cock, which will stand a smart blow without falling: while a slight touch applied to the trigger allows the spring to act.
Another example of the same state of constraint is the bologna phial - a glass cup with its sides thin, but bottom very thick. It also is cooled as quickly as possible. A bullet may be dropped into it with safety from a considerable height; but if a small sharp edged fragment of flint is dropped in, so as to scratch the surface in the slightest degree, the molecular forces are set free, and the whole falls to pieces.
Note: De la Bastie appears to be another name for these glass products.
Library of Universal Knowledge, American Book Exchange, New York, 1881, pp160, vol XII.
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"These Glass Drops are small parcels of coarse green Glass taken out of the Pots that contain the Metal (as they called it) in fusion, upon the end of an Iron Pipe; and being exceedingly hot, and thereby of a kind of sluggish fluid consistence, and are suffered to drop from thence into a Bucket of cold Water... Some of these I broke in the open air, by snapping off a little of the small stem with my fingers ... which I had no sooner done then the whole bulk of the drop flew violently, with a very brisk noise, into multitudes of small pieces" (Robert Hooke, Micrographia, 1667, vii, 33). Samuel Butler's Hudibras, John Wilders, Oxford, 1967, pp 384
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Steel (or iron for that matter) and glass are molten liquids that solidify on cooling. They can be tempered if immersed in water, oil or some other liquid. This act hardens the material and changes the working characteristics. In the case of steel, as example a knife or other blade, the steel becomes quite hard and is said to be tempered. Heating it again (as in the case of glass) causes it to ?lose? its temper and become soft and malleable.
Those who work glass recognize the need to cool the formed object slowly. Glass blowers turn off the oxygen to their torches causing a sooty flame which builds a black deposit on the glass surface. This shields the glass from sudden cooling and prevents development of stress within the glass which would cause it to crack or shatter.
jsw/08-06-2002
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