PART I

_THE PROJECTION OF LANTERN SLIDES_

_WITH ILLUSTRATIONS_

LONGMANS, GREEN, AND CO. 39 PATERNOSTER ROW, LONDON, E.C. FOURTH AVENUE & 30TH STREET, NEW YORK BOMBAY, CALCUTTA, AND MADRAS

1920

(_All rights reserved_)

* * * * *

{v}

PREFACE TO THE FIFTH EDITION

The first edition of this work was written by my father, the late Mr. Lewis Wright, and was published in 1890.

The reception that it received testified to the fact that it met a long-felt want, and successive editions were published in 1895, 1901, and 1906.

My father, unfortunately, met his death in a railway accident in 1905, and the corrections and additions to the last edition, which had been to a certain extent prepared by him, were completed and written by myself, and the work as published then was again reprinted in 1911.

As the original text is now thirty years old, it has seemed better entirely to re-write the whole book rather than make fresh revisions, the more so as the last ten years have seen great advances in the science of Lantern Projection, and especially in the developments of Acetylene and Electric Lighting.

It has also seemed best at the present juncture to issue the book in two parts, the first dealing with the Projection of Lantern Slides only, and the second with the Demonstration of Opaque and Microscopic Objects, Scientific Phenomena and accessory apparatus, including Cinematograph Projection.

It must of necessity be many months before this second volume can be produced, for the simple reason that Optical {vi} Instrument Makers have as yet hardly had time to turn round after the war and produce their new models, and therefore any such book written now could do little more than describe apparatus that was on the market prior to 1914.

The present work, therefore, deals solely with the exhibition of Lantern Slides in the Optical Lantern, and as such I trust will be found of value to Schoolmasters, Social Workers, Lecturers, and, in fact, to all who use the lantern as a means of illustration.

RUSSELL S. WRIGHT. _January 1920._

* * * * *

{vii}

CONTENTS

CHAPTER PAGE

I. INTRODUCTORY 1

II. THE ILLUMINANT 3

III. PARAFFIN-OIL LAMPS, INCANDESCENT GAS AND SPIRIT BURNERS 6

IV. THE ACETYLENE LIGHT 11

V. LIMELIGHT AND THE ACETYLENE BLAST 16

VI. THE ELECTRIC LIGHT 39

VII. THE OPTICAL SYSTEM OF A LANTERN 57

VIII. THE BODY OF THE LANTERN 70

IX. LANTERN BOXES, STANDS, READING LAMPS, ETC. 76

X. SCREENS AND SCREEN STANDS 79

XI. THE PRACTICAL MANIPULATION OF A LANTERN 82

{viii}

ILLUSTRATIONS

FIG. PAGE

1. Oil Lamp 6 2. Inverted Incandescent Lamp 8 3. Methylated Spirit Burner 9 4. Luna Lamp 10 5. The Moss Generator 12 6. The A.L. or 'Popular' Model 14 7. Acetylene Jet 15 8. Oxygen Cylinder in hemp cover 17 9. Double Lever Key 18 10. Fine Adjustment Valve 19 11. Construction of Beard's Regulator 20 12. Beard's Regulator 21 13. Regulator and Gauge 22 14. Gas-bags 24 15. 'Blow-through' Nozzles 25 16. 'Blow-through' Jet 25 17. Mixed Jet 27 18. Mixed Jet, Gwyer pattern 27 19. Mixing Chamber of Jet 28 20. 'Injector' Jet 30 21. 'Gridiron' Saturator 32 22. 'Pendant' Saturator 33 23. Fallot Air Blast 37 24. Fallot Air Blast, and Cylinder 37 25. Lime-tongs 39 26. Universal Hand-fed Arc Lamp 45 27. 46 28. Resistance 49 29. 'Scissors' Arc Lamp 51 30. 'Right-angled' Arc Lamp 52 31. 'Westminster' Arc Lamp 53 32. Arc Lamp with Induction Ring 56 33. The Optical System of a Lantern _facing p._ 57 33A. Optical System of Lantern 57 34. Optical System without Condenser 59 35. Action of Condenser 59 36. Forms of Condensers 60 37. Double Sliding Carrier 62 38. Beard's Dissolving Carrier 63 39. Focussing Action of Lens 64 40. Achromatic Lens 65 41. Petzval Combination 66 42. Hughes' Short-Range Lantern 71 43. Long-Range Lantern 72 44. Connections for a Bi-unial Lantern 73 45. Beard's Circulating Water Tank 75 46. Quadruple Lantern Stand 78 47. Reading Lamp 79 48. Roller Screen 80 49. Portable Screen Stand 81 50. Adjustment of the Light 84

* * * * *

{1}

OPTICAL PROJECTION

A TREATISE ON THE USE OF THE OPTICAL LANTERN