On a cold December evening in 1802,
在1802年12月的一个寒冷的晚上，
a nervous young man named Luke Howard stood before the assembled members of a London science club
一个紧张的、名为卢克·霍华德的年轻人，站在伦敦科学学会的成员面前，
about to give a lecture that would change his life and go on to change humanity's understanding of the skies.
将要发表一个会改变他人生的演讲，继而改变人类对天空的认识。
Luke Howard was a pharmacist by profession, but he was a meteorologist by inclination,
职业上，卢克·霍华德是一名药剂师，志趣上，他是一名气象学者，
having been obsessed by clouds and weather since childhood.
他从童年就对云和天气十分着迷。
As a school boy, he spent hours staring out of the classroom window, gazing at the passing clouds.
在学校时，他常常长时间地凝视窗外，盯着飘过的云。
Like everyone else at the time, he had no idea how clouds formed, or how they stayed aloft.
和那时所有人一样，他不知道云是怎样形成的，也不知道云怎么能漂浮在空中。
But he enjoyed observing their endless transformations.
但他乐此不疲地观察云朵无穷无尽的变化。
By his own admission, Luke paid little attention to his lessons,
据他自己承认，他几乎没花什么心思在课堂上，
but fortunately for the future of meteorology, he managed to pick up a good knowledge of Latin.
但幸运的是，从气象学未来的角度考虑，他掌握了足够的拉丁语知识。
Compared to the other natural sciences, meteorology, the study of weather,
与其他自然学科相比，气象学，研究天气科学，
was a late developer, mainly because weather is elusive.
发展得较晚，这主要是因为天气变幻莫测。
You can't snap off a piece of rainbow or a section of cloud for convenient study.
你无法摘下一小段彩虹或一小块云朵来进行研究。
You can, of course, collect rain water in calibrated containers, but all you really end up with are buckets of water.
你当然可以用精准的容器来收集雨水，但你最终得到的不过是一桶水。
Understanding clouds required a different approach, which is where Luke Howard's idea came in.
了解云朵，需要另一种途径，卢克·霍华德想出来一个主意。
His simple insight based on years of observation was that clouds have many individual shapes but they have few basic forms.
根据他对云朵多年的观察，他发现，虽然云有很多各不相同的形状，但基本的形式只有几种。
In fact, all clouds belong to one of three principle types to which Howard gave the names:
实际上，所有的云属于三种基本形式之一，霍德华给它们命名为：
cirrus, Latin for tendril or hair, cumulus, heap or pile, and stratus, layer or sheet.
卷云，来自于拉丁语中的卷须或头发；积云，堆积或积累；层云，层叠或片。
But that wasn't the clever part.
但这还不是他的高明之处。
Clouds are constantly changing, merging, rising, falling, and spreading throughout the atmosphere,
云是在不断变化的，合并，上升，下降，在整个大气中扩散，
rarely maintaining the same shapes for more than a few minutes.
相同的形状很少能维持几分钟。
Any successful naming system had to accommodate this essential instability, as Howard realized.
一套有效的命名系统，必须迎合云的不确定性，这是霍华德意识到的。

So, in addition to the three main cloud types,
所以，除了三种主要的形状的命名，
he introduced a series of intermediate and compound types as a way of including the regular transitions that occur among clouds.
他还给一系列由三种形状衍生或合成的云命名，这样便能概括常见的云的变形。
A high, whispy cirrus cloud that descended and spread into a sheet was named cirrostratus,
原本在高空中的纤薄的层云下降并且扩散成薄片状，被命名为卷层云，
while groups of fluffy cumulus clouds that joined up and spread were named stratocumulus.
由大量蓬松的积云聚集并扩散而成的则命名为层积云。
Howard identified seven cloud types, but these have since been expanded to ten,
霍华德一共命名了七种云，现在人们已将其扩展为十种，
cloud nine being the towering cumulonimbus thunder cloud,
第九种云是高耸的积雨云，
which is probably why being on cloud nine means to be on top of the world.
这或许是为什么“在第九种云上”有登上世界之巅的意思。
Howard's classification had an immediate international impact.
霍华德对云的分类当即在国际上产生了重大影响。
The German poet and scientist J.W. von Goethe wrote a series of poems in praise of Howard's clouds,
德国诗人和科学家约翰·沃尔夫冈·冯·歌德写了一系列的诗来赞美霍华德的云，
which ended with the memorable lines,
结尾，有难以忘怀的诗句：
'As clouds ascend, are folded, scatter, fall, Let the world think of thee who taught it all,'
“当云上升、层叠、扩散、下落，让世界想起你，这教导一切的人，”
while Percy Shelley also wrote a poem 'The Cloud,' in which each of Howard's seven cloud types was characterized in turn.
珀西·比希·雪莱也写过一首名为“云”是诗，在诗中，霍华德七种云中的每一种都被逐一描述。
But perhaps the most impressive response to the naming of clouds was by the painter John Constable,
但或许，在云被命名之后最令人难忘的举动，是画家约翰·康斯塔伯所做的，
who spent two summers on Hampstead Heath painting clouds in the open air.
他花了两个夏天在汉普西斯，在户外描画云朵。
Once they had been named and classified, clouds became easier to understand
自从云朵被命名和分类后，理解它们就变得容易了，
as the visible signs of otherwise invisible atmospheric processes.
通过可看见的云，我们能知道其他看不见的大气变化。
Clouds write a kind of journal on the sky that allows us to understand the circulating patterns of weather and climate.
云就像是天空的日记，通过云，我们可以了解天气和气候的循环模式。
Perhaps the most important breakthrough in understanding clouds
人类在对云的认识上所取得的最大突破，
was realizing that they are subject to the same physical laws as everything else on Earth.
应该是意识到云也遵循同一套物理定律，与其他在地球上的一切事物一样。
Clouds, for example, do not float, but fall slowly under the influence of gravity.
比如说，云，并不会飘浮，而是在重力的影响下慢慢下降。
Some of them stay aloft due to upward convection from the sun-heated ground,
有一些云飘浮在空中，是因为受到了太阳照射地面热气流上升的影响，
but most are in a state of slow, balletic descent.
但大部分云还是在优雅而缓慢地下降。
'Clouds are the patron goddesses of idle fellows,' as the Greek dramatist Aristophanes wrote in 420 B.C.
“云朵是懒汉的守护女神”，古希腊戏剧家阿里士多芬尼斯在公元前420年写下这句话，
and nephology, the study of clouds, remains a daydreamer's science,
而云学，仍然是一个爱做白日梦的人的科学，
aptly founded by a thoughtful young man whose favorite activity was staring out of the window at the sky.
恰巧由一个好思考的年轻人创立，他最爱做的事，便是出神地望着窗外的云朵。