Observations on fossil vegetables : accompanied by representations of their internal structure, as seen through the microscope / by Henry Witham.

  • Witham, Henry Thornton Maire, 1779-1844.
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: Observations on fossil vegetables : accompanied by representations of their internal structure, as seen through the microscope / by Henry Witham. 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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    Tlic slice must now be ground down to that degree of thinness which will permit its structure to be seen by help of a microscope. To facilitate this part of the grinding, the lapidary will find it advantageous to fix the glass in a groove made in a small piece of wood, of which half inch thick deal will answer the purpose. The groove in the wood should be a little less deep than the thickness of the glass, and the wood itself need not pro- ject more than half an inch beyond each side of the glass. A lapidary, by attending to the above directions, will find no difficulty in reducing any piece of petrified wood to that degree of thinness sufficient to render its structure visible; and any one, even without the aid of the me- chanism employed by the lapidary, may accomplish that object by attend- ing to the following directions. The position of the fibres of the wood having been ascertained, let a thin piece be chipped off by a blow of a hammer, in a direction perpendicular to the length of the fibres. Let the chip thus obtained be cemented to any small bit of wood by common lapidaries’ cement (a compound of 1 part bees’ wax, 1 part pitch, 4 parts rosin, 16 parts of a mixture of brick-dust and whitening), to enable the operator to hold it firmly while the grinding is going on. That side of the chip which approaches nearest to a perpendi- cular to the length of the fibres, must be ground flat, by giving it a rapid circular motion with the hand, on a piece of sheet-lead lying horizontally on a table, and supplied with a little emery, size No. 1., moistened with wa- ter. When the emery ceases to act, the muddy matter remaining may be removed, and a fresh portion of emery applied; and this must be repeated until the surface of the chip has become perfectly flat. The sheet of lead must then be removed, and a piece of flat sheet copper substituted, and the surface of the chip ground as smooth as may be, by flower of emery, freed from its coarser parts. The surface may then be polished by friction with crocus or rot-stone, on a transverse section of any soft wood. When the polishing is finished, the chip must be detached from the wood to which it was cemented, and the polished surface cemented by Ca- nada balsam to a piece of plate-glass, in the manner above described, and then ground thin, and polished as before.