Chapter I: Preface

To the meteorologist I hope the following pages may prove not only of some interest, but of practical value as a small step towards that greater exactness of language which is essential before we can attempt to explain all the details of cloud structure, or even interchange our ideas and observations with adequate precision. The varieties depicted and described have been selected from many hundreds, as those which seem to me to show such differences of form as to imply distinct differences in the conditions to which they are due. I have not attempted to deal with the physical causes of condensation except in a general way, being unwilling to introduce diagrams of isothermals and adiabatics and such purely scientific methods into a work also intended for a wider public. For those who wish to pursue this part of the subject I have appended a list of papers from the _Quarterly Journal of the Royal Meteorological Society_ and other sources, which may serve as references. I also hope that some more votaries of the science may be induced to realize that meteorology does not consist solely of the tabulation of long columns of records, but includes subjects for investigation as much more beautiful as they are more difficult.

To the artist I trust they may also be of some use, by calling attention to the variety and exquisite beauty of the sky. Nothing is more extraordinary in art than the general negligence of cloud-forms. Many of them are quite as worthy of careful drawing as the leaves of a tree, the flowers of a field, the ripples on a stream, or the texture of a carpet, or a marble pavement. Yet it is the common rule to find pictures, which are otherwise marvellous examples of skill and care, disfigured by impossible skies with vague, shapeless clouds, as untrue to nature as it would be possible to make them. Grace of outline, delicacy of detail and texture, richness of contrast, beauty of form and light and colour, all are present in the skies, and combine to make a whole well worthy of the best that art can give. The illustrations I offer are not selected for pictorial effect; they are chosen from a purely scientific point of view; but they are enough to indicate what could be done if the facts of nature were treated with high artistic skill.

In addition to the meteorologist and the artist, there are a much larger number who follow neither profession, but who love Nature in all her moods; and to them also I hope these pages may be of interest. Indeed, if only a few of them should be stimulated to take up a branch of nature study which has given me many an hour of quiet enjoyment, the labour of bringing these notes together will not have been in vain.

ARTHUR W. CLAYDEN.

St. John’s,
Exeter.

CONTENTS

CHAPTER PAGE

I. Introductory 1

II. Cirrus 21

III. Cirro-stratus and Cirro-cumulus 45

IV. Alto Clouds 59

V. Lower Clouds 71

VI. Cumulus 84

VII. Cumulo-nimbus 105

VIII. Wave Clouds 119

IX. Cloud Altitudes 137

X. Cloud Nomenclature 154

XI. Cloud Photography 165

References 181

Index 183

LIST OF ILLUSTRATIONS

PLATE PAGE

A Sunset Sky _Frontispiece_

1. Part of a Great Halo 22

2. Part of a Solar Halo 23

3. Cirro-nebula changing to Cirro-stratus 24

4. Cirro-nebula changing to Cirro-cumulus 27

5. High Cirrus. (_Cirrus Excelsus_) 31

6. Windy Cirrus. (_Cirrus Ventosus_) 32

7. Thread Cirrus. (_Cirro-filum_) 34

8. Tailed Cirrus. (_Cirrus Caudatus_) 35

9. Hazy Cirrus. (_Cirrus Nebulosus_) 36

10. Change Cirrus. (_Cirrus Inconstans_) 37

11. Common Cirrus. (_Cirrus Communis_) 40

12. Band Cirrus. (_Cirrus Vittatus_) 41

13. Band Cirrus. (_Cirrus Vittatus_) 42

14. Hazy Cirro-stratus. (_Cirro-stratus Nebulosus_) 46

15. Cirro-stratus 47

16. Cirro-stratus. (_Cirro-stratus Communis_) 48

17. Flocculent Cirro-stratus. (_Cirro-stratus Cumulosus_) 49

18. Cirro-stratus and Cirro-cumulus 50

19. Cirro-cumulus 50

20. Hazy Cirro-cumulus. (_Cirro-cumulus Nebulosus_) 51

21. Hazy Cirro-cumulus. (_Cirro-cumulus Nebulosus_) 51

22. A Sunset Sky 52

23. Speckle Cloud (Ley). (_Cirro-macula_) 53

24. Cirrus Caudatus and Cirro-macula 55

25. Alto-cumulus Informis 64

26. Hazy Alto-cumulus. (_Alto-cumulus Nebulosus_) 65

27. Flat Alto-cumulus. (_Alto-cumulus Stratiformis_) 65

28. High Turreted Cloud. (_Alto-cumulus Castellatus_) 66

29. High Ball Cumulus. (_Alto-cumulus Glomeratus_) 67

30. Mackerel Sky. (_Alto-stratus Maculosus_) 68

31. Mackerel Sky. (_Alto-stratus Maculosus_) 69

32. Alto-strato-cumulus 70

33. Sunset. (_Alto-cumulus Castellatus Fractus_) 70

34. Three Layers of Stratiform Cloud after Rain 73

35. Rain-Cloud. (_Nimbus_) 75

36. Rain-Cloud. (_Nimbus_) 75

37. Stratus Communis 77

38. Strato-cumulus 77

39. Strato-cumulus 78

40. Stratus Maculosus 78

41. Common Stratus. (_Stratus Communis_) 79

42. Roller Cloud. (_Stratus Radius_) 80

43. Small Cumulus. (_Cumulus Minor_) 94

44. Cumulus 95

45. Large Cumulus. (_Cumulus Major_) 96

46. Fracto-cumulus 97

47. Fall Cloud. (_Stratus Lenticularis_) 98

48. Thunder-clouds forming 109

49. Thunder-clouds. (_Cumulo-nimbus_) 110

50. Thunder-clouds. (_Cumulo-nimbus_) 111

51. Thunder-cloud. (_Cumulo-nimbus_) 111

52. Thunder-cloud. (_Cumulo-nimbus_) 111

53. The Flank of a Great Storm 112

54. Crested Alto Waves. (_Alto-cumulus Undatus_) 120

55. Alto Waves. (_Alto-stratus Undatus_) 121

56. Cirro Ripples. (_Cirro-cumulus Undatus_) 122

57. Waved Cirro-stratus. (_Cirro-stratus Undatus_) 136

58. Camera for measuring Altitudes 141

59. Print from a Negative used for measuring Altitude 144

60. Pair of Prints showing the Displacement of the Cloud 145

61. Cloud Camera for Studies 171

CLOUD STUDIES