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 CHAPTER I INTRODUCTORY