The book “Cloud Studies” was published in 1905, over a hundred years ago. It was written by Arthur W. Clayden, M.A., Former principal of University College, Exeter, UK. The book is available in PDF form since it’s out of copyright:
But the images are rather low quality, so I scanned them in from my copy of the 1925 edition (mostly the same photos), and I present them here:
It’s interesting that there are some clouds there that you might think look unnatural, or man made. But these photos were taken before powered flight was invented.
So if you are ever looking up at the sky, and you see a cloud that looks a little odd, and you are wondering if this is a recent phenomenon, then have a look back at what clouds were like in 1905. You’ll probably find your cloud here.
[Update March 23, 2011] I’ve also scanned in a good copy of the chapter on calculating cloud altitude using two cameras and the sun. This technique could easily (once the equations are worked out) be used to calculate the height of contrails, so would be highly recommended if you somehow suspect there’s some low-altitude spraying going on.
[Update Dec 12th, 2011]
High res scans of the 1905 version available on archive.org (in the HTTP section, the jp2 zip) The “read online” version is also very good.
Some of the photos were used in the earlier book CloudLand by William Clement Ley, 1894