Licence: Public Domain Mark
Credit: The atmosphere in relation to human life and health. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![Per cent. Motion of cirrus, last 23 Motion of cumulus, very slow 8 Vertical height of cumulus compared with breadth, great 73 A few waves or close ripples of well defined hard cirrus strata nearly overhead. 84 Length of steam trail, moderate (estimated 90 yards) 52 Color of clouds at dawn, pale yellow 58 Regular or irregular distribution of clouds (?) Regularity or variability of temperature and humidity in adjacent strata, etc. (?) [Probability of rain in twenty-four hours.] Visibility, great .- 70 Audibility, great 61 Humidity, difference of bulbs, 4 degrees 46 Humidity (increasing or diminishing), diminishing 29 High clouds, increasing 68 Cirrus (straight or tangled), tangled 81 Stars last night, much twinkling 71 Smoke, tending downward 69 Total 877 Probability, rain. The number of items in the forecast might be much increased with increasing knowledge, and the value of each, sign would also increase with continuous exact observation. Moreover, each sign should be studied not as a single item, but as occurring with otliers, and when considered in relation to others would gain mucli in value. Thus, visi- bility is not infrequent in fine dry weather, and also occurs in moist weather, before rain. If observed day after day in fine weather, its value in forecasting is evidently much less than when occurring in somewhat unsettled weather. In fact, each sign has properly a partic- ular value in particular kinds of Aveather, and the special value has to be ascertained. The length of time during which, a certain type of weather has continued is in some proportion to the probability of the ensuing days being of a similar type. When the total of the various percentages exceeds a certain fixed amount, the probability of bad weather rises to something approaching certainty, and perhaps the probability orf fine weather when the amount is minus goes a little further still. When, in addition, the probability announced by the central office from wide data is in the same direction, it becomes justifiable to place reliance on the forecasts for agricultural purposes and general district warnings. It will also eventually be of great use to farmers to have telegraphic information forwarded to dis- tricts toward which bad weather is moving, if there is reason to regard the change as more than local when first noticed. On some Possible Modifications of Climate by Human AOENCT.l There can be no doubt that some effect upon climate, shown more by physiological influences uj^on mankind than by instrumental records, • This section is derived from MS. written in 1891, but not in any way published.](https://iiif.wellcomecollection.org/image/b21208724_0154.jp2/full/800%2C/0/default.jpg)
