"The key idea set forth by Howard is that it was possible to identify, from within the complexity of changing skies, a number of simple categories. Howard's "genius" lay in the use of Latin names, thus transcending national boundaries.
The categories are:
1. Cumulus (L. for heap) Convex or conical heaps, increasing upward from a horizontal base.
2. Stratus (L. for layer) Widely extended horizontal sheet.
3. Nimbus (L. for rain) Systems of clouds from which rain falls.
4. Cirrus (L. for curl) Flexuous fibres extensible by increase in any or all directions.
With some minor adjustments in nomenclature, these are the categories and names used by meteorologists of all countries, 200 years later! This is a remarkable testimony to Howard's perceptive insight into cloud forms, the primary observable phenomena of meteorology." - Dr. John Day
Images of drawings from Luke Howard's sketch book courtesy of Cloudman.com