stry of its mystery in this, the land of its birth, cannot but
find justification. Although the theme is a favourite one with popular
lecturers, it is generally treated in a superficial way, leaving the
audience only in possession of the bare fact that dyestuffs, &c., have by
some means or other been obtained from coal-tar. I have endeavoured to go
somewhat beyond this, and to give some notion of the scientific principles
underlying the subject. If the reader can follow these pages, in which not
a chemical formula appears, with the same interest and with the same
desire to know more about the subject that was manifested by the audience
at the London Institution, before whom the lecture was delivered, my
object will have been accomplished. To the Board of Managers of that
Institution my thanks are due for the opportunity which they have afforded
me of attempting to extend that popular knowledge of applied science for
which there is such a healthy craving in the public mind at the present
time.

R. M.
_6 Brunswick Square, W.C._

CONTENTS.

CHAPTER I.

Origin of Coal, 9. Coal of various ages, 11. Graphite, 12. Recent
Vegetable Deposits, 13. Mode of occurrence of Coal, 13. Structure of Coal,
15. Uses of Coal, 16. Coal a source of Energy, 17. Mechanical Equivalent
of Heat, 19. Value of Coal as a Fuel, 20. Small efficiency of
Steam-engines, 21. Mechanical value of Coal, 22. Whence Coal derives its
Energy, 22. Chemical Composition of Coal, 23. Growth of Plants, 26. Solar
Energy, 28. Transformation of Wood into Coal, 30. Destructive Distillation
of Coal, 33. Experiments of Becher, 34; of Dean Clayton, 35; of Stephen
Hales, 37; of Bishop Watson, 37; of the Earl of Dundonald, 39. Coal-gas
introduced by Murdoch, 40. Spread of the new Illuminant, 41. Manufacture
of Coal-gas, 42. Quantitative results, 45. Uses of Coke, 47. Goethe's
visit to Stauf, 48. Bishop Watson on waste from Coke-ovens, 50. Shale-oil
Industry, 50. History of Coal-mining, 57. Introduction of Coal into
London, 58. The Coal resources of the United Kingdom, 60. Competition
between Electricity and Coal-gas, 62.

CHAPTER II.

Ammoniacal Liquor of Gas-works, 64. Origin of the Ammonia, 65. Ammonia as
a Fertilizer, 65. Other uses of Ammonia, 67. Annual production of Ammonia,
68. Utilization of Coal-tar, 69. The Creosoting of Timber, 70. Early uses
of the Light Tar Oils, 71. Discovery of Benzene by Faraday; isolation from
Tar Oil by Hofmann and Mansf