ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 341 



LIMITS OF THE ATMOSPHERE. 



The theoretical limits of the atmosphere; whether any portions are 

 being continually lost into space, and gained from space. 



ABSORPTION OF THE SPECTRUM. 



The absorption and reflection of various portions of the spectrum of 

 the atmosphere, by air and by vapors, at different heights. The con- 

 nection of radiation and absorption with states of weather and 

 approaching changes; diathermancy and translncency in connection 

 with forecasting. Absorption of several portions of the visible and 

 invisible spectrum in different states of the air. 



COMBINED FORECASTING-. 



An inquiry into and formulation of a plan for a combined system of 

 weather forecasting. In addition to the present schemes and practice 

 of weather forecast as used in Europe and America, it would seem 

 desirable to employ observation of local instruments and phenomena. 

 Trained observers are often able to make a more correct forecast for 

 their district from the appearance of the sky, etc., than they receive 

 from a central office. The training of observers is a necessary prelimi- 

 nary to a much more extended system of observation. The present 

 writer has proved that a great deal of use may be made of a number 

 of different signs taken in combination. Thus the character of a haze, 

 the superposition of currents, the exact character and appearance of 

 clouds and their edges, the length of trail of steam from a locomotive, 

 the color of the sky and sun, and of morning and evening clouds, the 

 radiation from an exposed thermometer, and the size and manner of fall 

 of raindrops, often give a fair prediction of coming weather. These 

 should be used in combination with the reports of barometric and other 

 instrumental readings from the various stations, and in aid of the estab- 

 lished system of data used for weather forecasts. Locally observed 

 phenomena, many of them not at present recognized as significant, 

 might, after a certain number of years' observation, have a definite 

 percentage value assigned to each as a prognostic, and the observer, 

 provided with a table of values, might then add up the percentages of 

 all the signs observed on each occasion, and from the total obtain a 

 very fair estimate of probability of coming weather over a district of 

 moderate area. The following table is intended to furnish an example 

 of such a system of local combined forecast, with imaginary figures : 



Station : Haslemere, Surrey, England. Time, 9 a. m. 



[Probability of rain in thirty-six hours.] 



Per cent. 

 Upper clouds, cirrus, cirro-cumulus, from west-northwest. Lower clouds, 



cumulus, from southwest 16 



Edges of cirro-cumulus, hard 27 



Edges of cumulus, rounded and hard 31 



