WUA THER-PR GNOSTICS. 65 5 



Suppose the cyclone stood still for a week, then the observer would 

 see a watery sky for a week, without any rain following. Suppose the 

 cyclone came on so far as to bring him under a watery sky, and then 

 died out or moved in another direction, then, after seeing a watery 

 sky, no rain would fall, but the sky would clear. The prognostic 

 would then be said to fail, but the word is only partially applicable. 

 The watery sky was formed and seen by the observer, because he was 

 in the appropriate portion of the cyclone, and so far the prognostic 

 told its story correctly — viz., that the observer was in the front of the 

 rainy area of a cyclone. The prognostic failed in its ordinary indica- 

 tion because the cyclone did not move on as usual, but died out, and 

 therefore never brought its rainy portion over the observer. This is 

 the commonest source of the so-called failure of a rain-prognostic in 

 Great Britain. The reason why all rain is not preceded by a watery 

 sky is because there are other sources of rain besides a cyclone, which 

 are preceded by a different set of weather-signs. Such is the whole 

 theory of prognostics. 



The same reasoning which applies to a watery sky holds good for 

 every other cyclone-prognostic. We shall have explained why any 

 prognostic portends rain when we have shown that the kind of sky or 

 other appearance which forms the prognostic belongs to the front of 

 the rainy portion of a cyclone. Conversely we shall have explained 

 why any prognostic indicates finer weather when we have shown that 

 the kind of sky belongs to the rear of a cyclone. It will be convenient, 

 therefore, to describe the weather in different parts of a cyclone, and 

 the appropriate prognostics together. 



First, to take those prognostics which depend on qualities common 

 to the whole front of the cyclone, viz., a falling barometer, increased 

 warmth and damp, with a muggy, uncomfortable feel of the air, and 

 a dirty sky. 



From the increasing damp in this part of a cyclone, while the sky 

 generally is pretty clear, cloud forms round and " caps " the tops of 

 hills, which has given rise to numerous local sayings. The reason is 

 that a hill always deflects the air upward. Usually the cold caused 

 by ascension and consequent expansion is not sufficient to lower the 

 temperature of the air below the dew-point ; but when very damp, the 

 same amount of cooling will bring the air below the dew-point, and so 

 produce condensation. 



From the same excessive damp the following may be explained : 

 " When walls are more than usually damp, rain is expected." The 

 Zuni Indians in New Mexico say that " when the locks of the Navajos 

 grow damp in the scalp-house, surely it will rain." From this we 

 may assume that scalps are slightly hygroscopic, probably from the 

 salt which they contain. Also, owing to excessive moisture, clouds 

 appear soft and lowering, and reflect the glare of iron-works and the 

 lights of large towns. 



