Hostname: page-component-8448b6f56d-dnltx Total loading time: 0 Render date: 2024-04-24T06:52:49.227Z Has data issue: false hasContentIssue false
  • English
  • Français

XVI.—The Sun as a Fog Producer

Published online by Cambridge University Press:  15 September 2014

John Aitken
Get access

Extract

I Fear that most, on reading the above title, will think it is either a printer's or an author's error, and that the title ought to have been “The Sun as a Fog Disperser.” We are familiar with the sun's power of clearing away fogs; we so often see fogs clear away as the sun rises, that we seem to have shut our eyes to another side of the question, which is, that under certain conditions the very opposite of this happens, the air thickening and fogging as the sun rises. Some years ago it was noticed at Falkirk, especially during the winter months, that on many mornings on which the air was clear before sunrise it gradually thickened to a dense haze, or to a dense fog, while in pure country air the observer never noticed similar changes. The question naturally suggested itself, what was the cause of this difference between the air at Falkirk and that of the country? A series of meteorological observations was therefore begun to ascertain whether this occasional fogging after sunrise was merely an accident, or if it had any connection with the sun; that is, to ascertain whether its appearance was what we call fortuitous, or if it appeared according to any law in nature.

Type
Proceedings
Information
Proceedings of the Royal Society of Edinburgh , Volume 32 , 1913 , pp. 183 - 215
Copyright
Copyright © Royal Society of Edinburgh 1913

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

page no 185 note * In the above table it will be noticed that in all but one case the force of the wind was less than 1 on the usual scale (1–12), that is, there was generally only a gentle drift. In the column under “Sunshine” 1 indicates a cloudless sky, that is, continuous sunshine.

page no 186 note * Proc. Roy. Soc. Edin., January 1893.

page no 187 note * An instance of the effect of local impurities on the formation of these fogs was seen on 23rd January of this year at Shandon, on the Gareloch. The wind during the night was very light and from the north, but fell calm in the morning, and the sky was cloudless. Over the whole Clyde area a dense fog formed, while over the Gareloch the air remained perfectly clear, the distant mountains being quite sharp. The only difference in the air over the two areas was that while the air over the Gareloch remained pure, that over the Glyde was much polluted by the products of the fires of the towns on the banks of the Clyde. The air over the Clyde might have been slightly warmer and damper than the other; but as the Gareloch is tidal, this difference can have been but slight.

page no 190 note * Proc. Roy. Soc. Edin., vol. xxx., Part IV., No. 3.

page no 195 note * Proc. Roy. Soc. Edin., vol. xxix., Part V., No. 30.

page no 196 note * I have previously advocated the filter method of purifying gases in place of bubbling them through solutions, as its effects are far more powerful than those of the ordinary one, which has a comparatively small action unless the gas has a very strong affinity for the contents of the solution; and even then it is far from being as perfect as the filtering process, and is practically useless for the experiments here described. Caustic solutions are not pleasant to work with, and the fingers may suffer if one attempts to pack the filter with wool soaked in caustic. The following method of preparing such a filter, however, presents no difficulties. The filter is first packed with cotton-wool, or any other suitable substance, in the dry state. The narrow end of the filter is then fitted into an india-rubber stopper which fits any bottle; an air-pump is also connected with the bottle. Some of the caustic solution is now poured into the upper open end of the filter and the pump worked. This draws the solution down through the cotton and thoroughly wets it. The pump should be worked quickly at the finish to draw out as much solution as possible, otherwise there will be bubbling produced by the filtered air, and nuclei made. These, however, may be checked by a second filter. The solution in the filter can be renewed when necessary in the same way.

page no 203 note * Proc. Roy. Soc. Edin., vol. xxxi. Part IV., No. 31.