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A universal goniometer

Published online by Cambridge University Press:  14 March 2018

A. Hutchinson
A. Hutchinson*
Affiliation:
University of Cambridge
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Extract

The instrument to be described in the following pages is a goniometer of the suspended type. It is intended primarily for tlle examination of small crystals, and by its aid all the usual crystallographic and optical determinations can be readily carried out. In its design the attempt has been made to combine efficiency with simplicity and strength of construction, together with adaptability to very various purposes. The instrument was completed in the spring of 1899, and has been in continuous use in the Mineralogical Laboratory at Cambridge ever since. Other instruments of the same general type were in existence at the time, or have been described during the past twelve years, and several features which were novelties when it was first constructed can no longer lay claim to originality.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 16 , Issue 74 , October 1911 , pp. 100 - 108
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1911

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References

Page 100 note 1 The instrument was constructed by Messrs. Troughton and Simms, 138 Fleet Street, London, at an approximate cost of £30. It has been briefly described in Tutton's, A. E. H. ‘Crystallography and Practical Crystal Measurement’, 1911, p. 765 Google Scholar, fig. 630.

Page 100 note 2 Vide H. A. Miers, Brit. Assoc. Report, 1894, 654 ; Zeits. Kryst. Min., 1904, vol. xxxix, p. 228 ; Leies, C., Zeits. Kryst. Min., 1899, vol. xxx, p. 363 Google Scholar.

Page 103 note 1 An excellent account of the method of adjusting a goniometer was given by Websky, M., Zeits. Kryst. Min., 1880, vol. iv, p. 545 Google Scholar. The essential points have been reproduced by Tutton, A. E. H. in his work ‘Crystallography and Practical Crystal Measurement’, 1911, p. 32 Google Scholar.

Page 104 note 1 The use of the Bertrand-lens for this purpose has also been recommended by de Souza-Brandão, V., Zeits. Kryst. Min., 1904, vol. xxxix, p. 583 Google Scholar, and by A. Hamberg, ibid., 1907, vol. xlii, pp. 13, 280.

Page 105 note 1 Zimányi, Vide K., Zeits. Kryst. Min., 1894, vol. xxii, p. 821 Google Scholar. A. J. Moses and E. Weinschenk, ibid., 1896, vol. xxvi, p. 150. C. Leiss, ibid., 1899, vol. xxx, p. 368. V. de Souza-Brandão, ibid., 1908, vol. xlv, p. 326.

Page 105 note 2 The tank can be procured from Mr. H. Helm, 66 Hatton Garden, London. The thermometer is best arranged to enter it at one side, and not, as shown in the figure, at the back.

Page 106 note 1 It is said that with this liquid an index of 1.83 can be attained; see Schroeder van der Kolk, ‘Tabellen zur mikroskopischen Bestimmung der Mineralion,’ 1906, p. 13. Personally I have not been able to go beyond 1.785.

Page 106 note 2 Directions for the preparation of Thoulet's solution and an exhaustive account of its physical properties have been given by V. Goldschmidt, Neues Jahrbuch Min., 1881, Beil.-Band i, pp. 179-238.

Page 106 note 3 The following device will be found convenient :—A narrow strip (20 mm. × 3 mm.) of thin glass of known optical properties is taken, one side polished plane and the other side ground. The crystal is attached at one end of the strip to the ground side, and the strip arranged vertically from the adjusting head G. After the critical angle for the crystal has been found, the plato is turned round, till the polished side of the glass becomes the reflecting surface and the critical angle is again determined.

Page 108 note 1 Similar eye-pieces suitable for use with petrological microscopes are supplied by Messrs. J. Swift & Son, 81 Tottenham Court Road, London, and will be found useful for a variety of purposes.

Page 108 note 2 Stöber, F., ‘Ueber ein einfaehes Theodolitgoniometer,’ Zeits. Kryst. Min., 1898, vol. xxix, p. 25 Google Scholar.