METEOROLOGY. 401 



It may not be presumptuous to add that if the idea of climate is- 

 to cover every kuown relation of the weather to human affairs, then 

 there are still many important features only lightly touched upon by 

 Hann that must be more fully considered than they have been even 

 in this introduction, which we have so fully analyzed in the preced- 

 ing lines. Some of these have indeed been taken up by the author 

 in his subsequent chapters on general or special climatology, and we 

 enumerate them here in order to direct attention to them, and at least 

 partially complete our enumeration of what data are called for in a 

 treatise on "climate." They are as follows: 



(1) Exhilarating and depressing weather is the effect of or may be 

 represented as a function of the simultaneous temperatures (t), wind(r), 

 barometric pressure (})), and relative humidity (/t), and is not fully ex- 

 pressed by the enumeration of the simply hot and moist days, but must 

 be determined by a special observation of the days in which the human 

 organism experiences such special feelings as are defined by the expres- 

 sions "closeness," "oppression," "weakening," "harshness," "rawness," 

 "penetrating," "chill," "mildness," "softness," "balmy," "soothing," 

 <* invigorating," "exhilarating," "stimulating," "nervous," "restless- 

 "ness," "gloominess," "cheerfulness," &c. In the absence of this per- 

 sonal or subjective record one may seek an approximate method by 

 calculating such an arbitrary function of /, v,p, h as will give numerical 

 results on a scale of to 10. Personal records of this character were 

 kept at Washington by J. W. Osborne and others as early as 1873. 



(2) The number of general storm-centers that pass over a locality, 

 and their general geographical distributions. As such storms are pre- 

 ceded by southeast to southwest winds, warmer, cloudy and rainy 

 weather, and followed by westerly winds, colder, clearing, drier weather, 

 their frequency is directly indicative of the changeableness of the cli- 

 mate, and presents in one datum a very concise summary of the features 

 that bear on health, business, domestic life, forestry, and commerce. 

 A map of storm frequency explains at a glance the distribution of north- 

 west and southwest winds in the United States, and the peculiarities 

 of our climate as given by Hann on page 556. Such charts were at- 

 tempted by Espy in 1836, but actually compiled first by the present 

 writer for the statistical atlas of the United States Ninth Census, Wash- 

 ington, 1874. A general review for Europe and America has recently 

 been given by Koppen. 



(3) The frequency of severe local storms, such as the tornadoes of the 

 United States. (A first attempt at collecting these data is given by 

 Finley. Professional Papers Signal Service jSTo. 4.) 



(4) The frequency of calms as causing poor ventilation, and being 

 accompanied by stagnant or unwholesome air. 



(5) The durations of twilight and the general color of the sky by day, 

 and the special colors at sunrise and sunset, as indicative of the reflec- 

 tion, transmission, and absorption of the solar radiation. In the tropics, 



